Many chemicals released into the environment are believed to disrupt normal endocrine functions in humans and animals. These endocrine disrupting chemicals (EDCs) affect reproductive health and development. A major group of EDCs that could be responsible for reproductive effects are those that mimic natural oestrogens, known as xeno-oestrogens. A number of in vivo and in vitro screening strategies are being developed to identify and classify xeno-oestrogens, in order to determine whether they pose a health risk to humans and animals. It is also important to be able to apply the assays to environmental samples for monitoring purposes. In South Africa information on the levels of EDCs in water is limited. While establishing the recombinant yeast screen bioassay (RCBA) using the yeast strain Sacchyromyces cerivisiae for oestrogenic activity, problems were experienced with contamination. Four South African laboratory water sources were assessed. From the results it was clear that the water used in the preparation of the medium for the assay was the source of oestrogenic contamination. Care should be taken to eliminate all possible sources of contamination in the test procedures to eliminate the reporting of false positive results. The fact that South African laboratory and surface waters tested positive for estrogenic activity has far reaching implications regarding reproductive and general health.

<p>'Endocrine disrupting chemicals (EDCs) are compounds found in the environment that have the potential to disrupt normal endocrine function. Estrogenic EDCs (e-EDCs) is a subclass of EDCs and is defined as substances contaminating the environment that may mimic or inhibit the effect of endogenous estrogen and therefore may influence developmental and reproductive health in humans and animals. The aim of this study was to develop, validate and implement a battery of in vitro and in vivo screening assays for e-EDCs. The study was concluded by implementing this battery of assays to assess the Eerste River, South Africa at three sampling sites, namely Jonkershoek, Stellenbosch sewage treatment works (STW) effluent and Spier for e-EDCs. The control site, Jonkershoek contained very low levels of estrone. Water from this site showed no estrogenic activity when the E-screen and the ER_ induction in MCF-7 cells. Some of the water samples collected at this site tested positive for estrogenicity when analysed with the juvenile tilapia VTG assay, whereas the rest were negative. The estrone levels in the sewage effluent extracts as well as Spier were significantly higher. The assay using ER_ protein induction by the MCF-7 cell line, the MCF-7 proliferation assay and the tilapia in vivo screen for estrogenicity showed that these samples are estrogenic. Results obtained for estrogenicity at the three different sampling sites for each of the assays in the battery were comparable. In this study we developed, validated and also implemented a battery of assays encompassing both in vitro and in vivo assays, based on different biological mechanisms, to detect estrogenic EDCs. To our knowledge, this is the first study that has used a battery of bioassays to specifically assess a South Africa river for estrogenicity...'</p>

No description available.

No description available.

No description available.

Cholecystokinin, or "CCK" peptides, originally identified in the gastrointestinal tract, are now considered to be one of the most abundant peptide systems in the mammalian central nervous system. Prompted by recent findings that implicated the cholecystokinergic system in the pathophysiology of various illnesses, we developed a novel assay system to measure the various forms of cholecystokinin peptides in human plasma and cerebrospinal fluid. The system detects CCK-4, sulfated CCK-8 (CCK-8s) and nonsulfated CCK-8 (CCK-8ns) with equal affinity, with the lower detection limit of 2.7 fmol and an ED50 of 10.6 +/- 2.2 fmol. Using the assay system, we determined that mean CCK-like immunoreactivity (CCK-LI) in the plasma of 12 healthy subjects was 12.9 +/- 2.1 pM CCK-4 equivalents. / After developing the cholecystokinin assay system, we were able to combine our unique methodology with other established techniques to investigate the role of CCK in illnesses such as premenstrual dysphoric disorder (PMDD), anxiety, bulimia nervosa, and cardiomyopathy. / Briefly, we observed no significant differences in plasma CCK levels between women with PMDD and healthy volunteers. However, we found that, independent of diagnosis, plasma cholecystokinin concentrations were higher in women during their first visit to the clinic to participate in the study, as compared to later visits. / In addition, application of our assay system allowed us to determine that oral ingestion of caffeine increased plasma CCK-LI levels 2--4 fold in humans. Moreover, we observed substantial variation in post-caffeine cholecystokinin levels among individuals. / In another study of cholecystokinin and anxiety, we used our CCK assay to determine the effects of ondansetron, a serotonin receptor antagonist, on cholecystokinin levels in plasma. We found that multiple oral doses of ondansetron influence the pharmacokinetic parameters of exogenous CCK. / We also used the three-step assay system to measure CCK-LI in patients with the eating disorder, bulimia nervosa. Baseline fasted cholecystokinin plasma levels were lower in bulimic women as compared to control subjects. However, at "satiety", or the post-binge stage, CCK levels in bulimic women were similar to those of control women. / Finally, our investigation into the role of cholecystokinin in cardiomyopathy revealed that neuronal cholecystokinin receptor density was altered in the cardiomyopathic hamster brain, as compared to age- and sex-matched control animals. (Abstract shortened by UMI.)

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 10 uppsatser.

Thesis (M.S.)--Villanova University, 2008. / Biology Dept. Includes bibliographical references.

Thesis (M.S.)--Villanova University, 2008. / Biology Dept. Includes bibliographical references.