Sr/Ca ratios indicate frugivory versus folivory in primates: a case study using handheld XRF in Kibale National Park, Uganda.

Researchers often use trace element concentrations, including strontium-calcium ratios (Sr/Ca), to reconstruct paleodiets. While most commonly used as a proxy for meat consumption, a more appropriate application may be to differentiate frugivory from folivory. Sr/Ca ratios in animal tissue reflect the Sr/Ca ratios of the highest calcium components of that animal's diet. Because plants have much higher concentrations of calcium than meat, meat consumption signals are often overwhelmed by the variation in Sr/Ca ratios coming from different plant parts. This study uses faunal and plant data from Kibale National Park, a protected forest in southwestern Uganda home to numerous primate species (for example, common chimpanzees and baboons), to assess the reliability of Sr/Ca ratios to differentiate between primate dietary groups. We find that leaves consistently have higher strontium and calcium concentrations than fruits and that this is mirrored in higher Sr/Ca ratios in folivorous primates compared to frugivorous primates. Plant species differ widely in both their overall Sr/Ca ratios and the differences between their fruit and leaf Sr/Ca ratios, but this variation does not overwhelm the dietary signal separating frugivores and folivores. Furthermore, this research demonstrates that non-destructive and portable X-ray florescence (XRF) methods are an effective means of gathering Sr/Ca data from plant and faunal material, increasing the opportunities to apply such methods to fossil material in the future.

Adaptation of the Boyden chamber to flow conditions: rheological effects on chemotaxis.

Although standard Boyden chambers assess chemotaxis under static fluid conditions they are routinely used as an experimental system to model the dynamic events associated with leukocyte extravasation in vivo. We have adapted the Boyden chamber system by incorporating it within the confines of a cone and plate viscometer which can then be employed to generate known shear conditions as the chemotactically responding cells migrate. Our results show that random locomotion of rat peritoneal exudate cells is stimulated under shear conditions within the range of 11.25-90/s relative to that under static conditions. Furthermore, chemotaxis to the synthetic tripeptide F-Met-Leu-Phe (FMLP) is also stimulated under shear conditions with the peak effect occurring near 22.5/s. This adaptation of the standard chamber system to allow the study of chemotaxis under flow conditions may provide further insight on the migratory properties of leukocytes in vivo.

Phagocytic properties of cultured murine trophoblast.

The phagocytic potential of cultured trophoblast from early (ectoplacental cone (EPC); day 7.5 post coitum) and mid-term (placenta; day 12 to 14 post coitum) pregnancy in the mouse has been examined using a variety of test particles and culture conditions. In suspension, small numbers (less than 1 per cent) of large placental trophoblast cells showed limited phagocytic uptake of Staphylococcus aureus but not of opsonized sheep red blood cells (RBCs). In contrast, trophoblast phagocytosis was never seen in monolayer placental cell culture. Placental macrophages consistently exhibited phagocytic uptake of both opsonized sheep RBCs and S. aureus under these conditions. In monolayer culture, EPC trophoblast phagocytosed S. aureus, but there was only limited uptake of RBCs (mouse or sheep) or spermatozoa. When cultured in a three-dimensional matrix (blood and plasma clots), however, EPC trophoblast demonstrated extensive phagocytosis of both RBCs and sperm. These results are discussed with reference to the use of in vitro systems for examining developmental processes, and a possible role for trophoblast phagocytosis in early gestation is proposed.

Transferrin receptor expression in early postimplantation mouse trophoblast and associated tissues.

The expression of the transferrin receptor (TR) was examined on murine trophoblast cells on days 6, 8 and 10 of gestation, using a monoclonal antibody visualized by indirect immunofluorescence on cryostat sections of the implant site. In the day 6 tissues, TR were observed on both the ectoplacental cone (EPC) and mural giant cell trophoblast populations, as well as on the embryonic ectoderm, anti-mesometrial decidual cells, uterine glandular epithelium and myometrium. By the 8th day of gestation, TR expression was weak, or undetectable on trophoblast giant cells (TGC), but remained strong on the proliferating cells of the EPC and embryo. In the definitive placenta (day 10), TR are expressed primarily on the differentiated labyrinthine trophoblast cells involved in the maternal-fetal transfer of iron.

GM-CSF and CSF-1 stimulate DNA synthesis but not cell proliferation in short-term cultures of mid-gestation murine trophoblast.

Short-term cultures of purified murine trophoblast were used to investigate the potential trophic effects of a number of cytokines. Both granulocyte-macrophage colony stimulating factor (GM-CSF) and colony stimulating factor-1 (CSF-1) increased [3H]thymidine (TdR) uptake (3-8 times control values) by trophoblast harvested from placentae on day 12 or 14 of pregnancy. In contrast, interleukin-3 (IL-3) had only a mild stimulatory effect ([3H]TdR uptake 1.5 times control), and IL-2 did not alter the level of DNA synthesis in these cells. Immunocytochemical analysis confirmed that the cells engaged in DNA synthesis were cytokeratin-positive trophoblast cells and revealed that these cells predominantly bore markers (alkaline phosphatase, transferrin receptors) characteristic of trophoblast cells from the placental labyrinth. The increased DNA synthesis observed after exposure to GM-CSF or CSF-1 was not associated with a change in the proportion of nuclei involved in synthesis, nor did it result in significantly increased trophoblast cell numbers in the cultures. These findings suggest that DNA-synthesizing trophoblast cells were not proliferating, but were more likely engaged in endoreduplicative cycles leading to the formation of terminally differentiated trophoblast giant cells. These results caution against the presumption of proliferation when measuring [3H]thymidine incorporation by placental or trophoblast cells in standard in vitro cultures. In addition, taken together with the reports of high levels of CSF-1 in the pregnant uterus and the expression of the CSF-1 receptor on placental trophoblast cells, they suggest that the hemopoietic cytokines may play a role in the differentiation and/or function of trophoblast cells in the developing murine placenta.

Murine trophoblast cells are not killed by tumor necrosis factor-alpha.

Purified midgestation murine trophoblast cannot be killed by a variety of cell-mediated effector mechanisms, with the exception of highly lytic effectors such as lymphokine-activated killer cells. We now report that this trophoblast population is also resistant to tumor necrosis factor (TNF)-alpha.

Murine trophoblast can be killed by allospecific cytotoxic T lymphocytes generated in GIBCO Opti-MEM medium.

Previous work in this laboratory demonstrated that a population of cultured midterm murine trophoblast cells are not susceptible to lysis by allospecific cytotoxic T lymphocytes (CTL) generated by standard in vitro protocols. We now report that this trophoblast population is killed, in an MHC-dependent manner, by allospecific CTL generated in GIBCO Opti-MEM, a modified tissue culture medium designed to maintain cell growth and proliferation in the presence of low concentrations of fetal bovine serum (FBS).

Class I major histocompatibility complex antigen expression on early murine trophoblast and its induction by lymphokines in vitro. II. The role of gamma interferon in the responses of primary and secondary giant cells.

The induction of paternal Class I and II MHC antigens by crude lymphokine preparations or purified recombinant gamma interferon was investigated on (C57BL/6J X CBA/H)F1 primary and secondary trophoblast giant cell outgrowths from 3.5-day post-coital (pc) blastocyst and 7.5-day pc ectoplacental cone preparations, respectively, using sensitive immunogold labelling techniques and electron microscopy. Class I MHC (but not Class II) antigens could readily be induced on secondary trophoblast giant cells, by incubation in vitro with gamma interferon for 40 h. However, repeated attempts to induce detectable MHC antigens on primary trophoblast giant cells failed. Mock-treated (C57BL/6J X CBA/H)F1 secondary trophoblast giant cell control preparations failed to express detectable MHC antigens. These findings suggest that, at the time of implantation, there is a time window during which MHC antigens are neither expressed constitutively nor are inducible by soluble factors which normally modulate cell surface MHC antigen concentration.

Class I major histocompatibility complex antigen expression on early murine trophoblast and its induction by lymphokines in vitro.

The expression of paternal class I and class II major histocompatibility complex (MHC) antigens in cultures of murine ectoplacental cone trophoblast was examined using immunogold labelled antibodies and electron microscopy. Class I MHC antigens could be induced on ectoplacental cone derived trophoblast following exposure to concanavalin A stimulated T cell supernatants. Class I MHC antigens were not detected in untreated trophoblast cultures. Class II MHC antigens were never detected on trophoblast whether treated or untreated. This is the first report of the experimental induction of Class I MHC antigens on a population of normally MHC-negative trophoblast cells.

Major histocompatibility antigens on trophoblast and their regulation: implications in the maternal-fetal relationship.

Recent technological advances have provided methods of detecting antigens encoded by the major histocompatibility complex with greater precision, allowing the expression of such antigens on the components of the placenta to be clarified. Of specific interest is the expression of these antigens on trophoblast cells, the fetal-derived epithelial cells that confront maternal blood and tissues at the maternal-fetal interface. It is now clear that the different trophoblast subpopulations differentially express class I antigens, although none appear to express class II antigens. Class I antigens can be induced by exposure to interferons on some populations but apparently not others, suggesting that the regulation of their expression differs for subpopulations of trophoblast cells, depending on gestational stage and location. This restricted expression has important implications for maternal-fetal immune interactions during the different phases of pregnancy and perhaps also bears on physiological functions of the feto-placental unit, such as growth and differentiation.