DEFECT ELECTRONIC STATES IN BETA-CAROTENE AND LOWER HOMOLOGS

We present semi-empirical calculations of the atomic geometries and electronic charge distributions of beta-carotene homologues of different chain lengths. We find defects in charged and photoexcited chains that are similar to the defects found in the degenerate polymer trans-polyacetylene, and we show how confinement affects these defects as the chains we shortened. Our results exhibit a generalized form of charge-conjugation symmetry in which the properties of a negatively charged defect are related to those of a positive one and vice versa

Cervical synovial sarcoma in a young boy

Synovial sarcomas comprise about 8% of all tumours of somatic soft-tissues, and are the most common sarcomas of the 'hands and feet. Occasionally they may occur in the trunk, but they have rarely been reported in the neck. We present a case of cervical soft-tissue mass producing symptoms in a 12-year-old-boy. This mass could be defined partially by radiological techniques, but its nature was not suspected because of its rarity in children and particularly in view of its unusual site.S. Afr. Med. J 48, 2181 (1974)

Human placental cytotrophoblasts produce the immunosuppressive cytokine interleukin 10.

The mechanism by which the mammalian mother accepts the implanting fetus as an allograft remains unexplained, but is likely to be the result of a combination of factors. Mononuclear cytotrophoblasts, the specialized fetal cells of the placenta that invade the uterus, play an important role. These cells express HLA-G, an unusual major histocompatibility complex class I-B molecule, and secrete cytokines and pregnancy-specific proteins that can regulate immune function. We investigated whether cytotrophoblasts secrete interleukin 10 (IL-10), a cytokine that potently inhibits alloresponses in mixed lymphocyte reactions. Cytotrophoblasts from all stages of pregnancy produced IL-10 in vitro, but neither placental fibroblasts nor choriocarcinoma (malignant trophoblast) cell lines did so. Spontaneous IL-10 production averaged 650, 853, and 992 pg/10(6) cells in the first, second, and third trimesters of pregnancy, respectively. IL-10 secretion dropped approximately 10-fold after the first 24 h of culture, and was paralleled by a decrease in messenger RNA. IL-10 messenger RNA was detected in biopsies of the placenta and the portion of the uterus that contains invasive cytotrophoblasts, suggesting that this cytokine is also produced in vivo. IL-10 secreted by cytotrophoblasts in vitro is bioactive, as determined by its ability to suppress interferon gamma production in an allogeneic mixed lymphocyte reaction. We conclude that human cytotrophoblast IL-10 may be an important factor that contributes to maternal tolerance of the allogeneic fetus

Wear simulation of a polyethylene-on-metal cervical total disc replacement under different concentrations of bovine serum lubricant

Metal-on-polyethylene total disc replacements have been an alternative to spinal fusion in the lumbar spine under certain indications for more than a decade. Recently, cervical total disc replacement has also become an alternative to cervical fusion. Knowledge acquired from years of in vitro simulator studies on other joint replacements has highlighted the risks associated with premature wear due to unforeseen adverse clinical conditions and the effect of particulate debris on surrounding natural tissues. Having no evidence of the type and composition of the lubricating fluid that will result after spinal arthroplasty, a study on the effects of lubricant serum concentration was undertaken. The wear rate was shown to be inversely proportional to protein content of the serum over a range of 50%–3% bovine serum to water concentration

Gestational and lactational exposure of rats to xenoestrogens results in reduced testicular size and sperm production

EHP is a publication of the U.S. government. Publication of EHP lies in the public domain and is therefore without copyright. Research articles from EHP may be used freely; however, articles from the News section of EHP may contain photographs or figures copyrighted by other commercial organizations and individuals that may not be used without obtaining prior approval from both the EHP editors and the holder of the copyright. Use of any materials published in EHP should be acknowledged (for example, "Reproduced with permission from Environmental Health Perspectives") and a reference provided for the article from which the material was reproduced.This study assessed whether exposure of male rats to two estrogenic, environmental chemicals, 4-octylphenol (OP) and butyl benzyl phthalate (BBP) during gestation or during the first 21 days of postnatal life, affected testicular size or spermatogenesis in adulthood (90-95 days of age). Chemicals were administered via the drinking water or concentrations of 10-1000 micrograms/l (OP) or 1000 micrograms/l (BBP), diethylstilbestrol (DES; 100 micrograms/l) and an octylphenol polyethoxylate (OPP; 1000 micrograms/l), which is a weak estrogen or nonestrogenic in vitro, were administered as presumptive positive and negative controls, respectively. Controls received the vehicle (ethanol) in tap water. In study 1, rats were treated from days 1-22 after births in studies 2 and 3, the mothers were treated for approximately 8-9 weeks, spanning a 2-week period before mating throughout gestation and 22 days after giving birth. With the exception of DES, treatment generally had no major adverse effect or body weight: in most instances, treated animals were heavier than controls at day 22 and at days 90-95. Exposure to OP, OPP, or BBP at a concentration of 1000 micrograms/1 resulted in a small (5-13%) but significant (p < 0.01 or p < 0.0001) reduction in mean testicular size in studies 2 and 3, an effect that was still evident when testicular weight was expressed relative to body, weight or kidney weight. The effect of OPP is attributed to its metabolism in vivo to OP. DES exposure caused similar reductions in testicular size but also caused reductions in body weight, kidney weight, and litter size. Ventral prostate weight was reduced significantly in DES-treated rats and to minor extent in OP-treated rats. Comparable but more minor effects of treatment with DES or OP on testicular size were observed in study 1. None of the treatments had any adverse effect on testicular morphology or on the cross-sectional area of the lumen or seminiferous epithelium at stages VII-VIII of the spermatogenic cycle, but DES, OP, and BBP caused reductions of 10-21% (p < 0.05 to p < 0.001) in daily sperm production. Humans are exposed to phthalates, such as BBP, and to alkylphenol polyethoxylates, such as OP, but to what extent is unknown. More detailed studies are warranted to assess the possible risk to the development of the human testis from exposure to these and other environmental estrogens

Effect of neonatal exposure to estrogenic compounds on development of the excurrent ducts of the rat testis through puberty to adulthood.

Neonatal exposure to diethylstilbestrol (DES) can alter the structure of the testicular excurrent ducts in rats. We characterized these changes according to dose and time posttreatment and established whether potent estrogens (ethinyl estradiol), environmental estrogens (genistein, octylphenol, bisphenol A, parabens), and tamoxifen induce such changes. Rats were administered these compounds neonatally and assessed at several time points during (day 10, or day 18 for some treatments) and after (days 18, 25, 35, and 75) the treatment period to detect any changes in testis weight, distension of the rete testis and efferent ducts, epithelial cell height in the efferent ducts, and immunoexpression of the water channel aquaporin-1 (AQP-1). Treatment with DES (10, 1, or 0.1 microg/injection; equivalent to 0.37, 0.037, or 0.0037 mg/kg/day, respectively) induced dose-dependent changes in testis weight and all parameters. These effects were most pronounced at days 18 and 25 and appeared to lessen with time, although some persisted into adulthood. Neonatal treatment with ethinyl estradiol (10 microg/injection; equivalent to 0.37 mg/kg/day) caused changes broadly similar to those induced by 10 mg DES. Administration of tamoxifen (2 mg/kg/day) caused changes at 18 days that were similar to those induced by 1 microg DES. Treatment with genistein (4 mg/kg/day), octylphenol (2 mg/injection; equivalent to 150 mg/kg/day), or bisphenol A (0.5 mg/injection; equivalent to 37 mg/kg/day) caused minor but significant (p<0.05) decreases in epithelial cell height of the efferent ducts at days 18 and/or 25. In animals that were followed through to 35 days and/or adulthood, these changes were no longer obvious; other parameters were either unaffected or were affected only marginally and transiently. Administration of parabens (2 mg/kg/day) had no detectable effect on any parameter at day 18. To establish whether these effects of estrogens were direct or indirect (i.e., resulting from reduced follicle-stimulating hormone/luteinizing hormone secretion), the above end points were assessed in animals in which gonadotropin secretion was suppressed neonatally by administration of a gonadotropin-releasing hormone antagonist. This treatment permanently reduced testis weight, but did not affect any of the other end points, apart from a minor transient reduction in efferent duct epithelial cell height at 18 days. This study suggests that structural and functional (expression of AQP-1) development of the excurrent ducts is susceptible to impairment by neonatal estrogen exposure, probably as a consequence of direct effects. The magnitude and duration of adverse changes induced by treatment with a range of estrogenic compounds was broadly comparable to their estrogenic potencies reported from in vitro assays

Non-destructive monitoring of viability in an ex vivo organ culture model of osteochondral tissue

Organ culture is an increasingly important tool in research, with advantages over monolayer cell culture due to the inherent natural environment of tissues. Successful organ cultures must retain cell viability. The aim of this study was to produce viable and non-viable osteochondral organ cultures to assess the accumulation of soluble markers in the conditioned medium for predicting tissue viability. Porcine femoral osteochondral plugs were cultured for 20 days, with the addition on day 6, of Triton X-100 (to induce necrosis), camptothecin (to induce apoptosis) or no toxic additives. Tissue viability was assessed by the tissue destructive XTT (sodium 3'-[1-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzene-sulfonic acid hydrate) assay method and LIVE/DEAD® staining of the cartilage at days 0, 6 and 20. Tissue structure was assessed by histological evaluation using haematoxylin & eosin and safranin O. Conditioned medium was assessed every 3-4 days for glucose depletion, and levels of lactate dehydrogenase (LDH), alkaline phosphatase (AP), glycosaminoglycans (GAGs), and matrix metalloproteinase (MMP)-2 and MMP-9. Necrotic cultures immediately showed a reduction in glucose consumption, and an immediate increase in LDH, GAG, MMP-2 and MMP-9 levels. Apoptotic cultures showed a delayed reduction in glucose consumption and delayed increase in LDH, a small rise in MMP-2 and MMP-9, but no significant effect on GAGs released into the conditioned medium. The data showed that tissue viability could be monitored by assessing the conditioned medium for the aforementioned markers, negating the need for tissue destructive assays. Physiologically relevant whole- or part-joint organ culture models, necessary for research and pre-clinical assessment of therapies, could be monitored this way, reducing the need to sacrifice tissues to determine viability, and hence reducing the sample numbers necessary

Sign-reversal of the in-plane resistivity anisotropy in hole-doped iron pnictides

The in-plane anisotropy of the electrical resistivity across the coupled orthorhombic and magnetic transitions of the iron pnictides has been extensively studied in the parent and electron-doped compounds. All these studies universally show that the resistivity $\rho_{a}$ across the long orthorhombic axis $a_{O}$ - along which the spins couple antiferromagnetically below the magnetic transition temperature - is smaller than the resistivity $\rho_{b}$ of the short orthorhombic axis $b_{O}$, i. e. $\rho_{a}<\rho_{b}$. Here we report that in the hole-doped compounds Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$, as the doping level increases, the resistivity anisotropy initially becomes vanishingly small, and eventually changes sign for sufficiently large doping, i. e. $\rho_{b}<\rho_{a}$. This observation is in agreement with a recent theoretical prediction that considers the anisotropic scattering of electrons by spin-fluctuations in the orthorhombic/nematic state.Comment: This paper has been replaced by the new version offering new explanation of the experimental results first reported her