Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 3

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

Search:
in the keywords:  furan
help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

The influence of perinatal and current dioxin and PCB exposure on puberty: a review

100%
Leijs M. M., van der Linden L. M., Koppe J. G., de Voogt P., Olie K., van Aalderen W. M. C., ten Tusscher G. W.
Biomonitoring
|
2014
|
vol. 1
|
issue 1
EN
Over the last two decades much has been written about the consequences of perinatal dioxin and PCB exposure in humans. In this paper we strive to elucidate the data on puberty in relation to these endocrine disruptive compounds in human populations. Effects in PCB/dioxin-exposed human populations on puberty are seen, not only in highly exposed cohorts, but also in average populations with background exposures. Study showed effects like increased weight, a delay in pubic hair growth and male genital development in boys, sex-hormone homeostasis, reduced penile length, and delayed age at first ejaculation after PCB exposure. Effects seen after dioxin exposure include retarded initiation and stage of breast development in girls, earlier menarche, disruption of sex hormone homeostasis, reduced testicular volume and reduced penile length in boys. The data published by different studies were inconclusive as a result of different methodological setup as well as because of multiple exposure settings. Populations were exposed to different mixtures of dioxin/PCB congeners or mixtures with other endocrine disrupters, and therefore synergistic and antagonistic effects with PCBs and dioxins are possible. Dioxinlike compounds disturb the hormonal balance mainly through interaction with the Ah receptor, which may influence the synthesis of hormones or their transport proteins. However, we have to keep in mind that hormonal balance during puberty could also be altered by disruption of the thyroid homeostasis. Another important possible mechanism is the induction of epigenetic changes or effects on genetic polymorphism. The fact that exposure to background concentrations of dioxin-like compounds and PCBs also has effects on the reproductive development is disconcerting and warrants further research and long term follow-up studies.
2
Content available remote

Enhancement of molecular polarizabilities by the push-pull mechanism; a DFT study of substituted benzene, furan, thiophene and related molecules

67%
Hinchliffe A., Mkadmh A., Nikolaidi B., Soscún H., Abu-Awwad F.
Open Chemistry
|
2006
|
vol. 4
|
issue 4
743-759
EN
We report Density Functional Theory (DFT) studies of the dipole polarizabilities of benzene, furan and thiophene together with a number of substituted and related systems. All geometries were optimized (and characterized) at the B3LYP/6-311g(2d,1p) level of theory and polarizabilities then calculated with B3LYP/6-311++G(2d,1p). For the R-ring systems we find group polarizabilities in the order R = NO2 ∼ OCH3 ∼ CN ∼ CHO > NH2 > OH > H = 0. For systems R-ring-R, 〈α〉 differs little from the additivity model, with small positive and negative increments. For systems D-ring-A (where D and A are deactivating and activating groups) we find a positive enhancement to 〈α〉 over and above the value expected on the basis of pure additivity for all pairs A and D studied. This enhancement can be increased greatly by extending the length of the conjugated chain to D-ring-CH=CH-ring-A and D-ring-N=N-ring-A systems. Empirical models of polarizability such as AM1 agree badly with the DFT calculations in an absolute sense but give excellent statistical correlation coefficients. Calculated 〈α〉’s also agree well in a statistical sense with the molecular volumes calculated from molecular mechanics force fields Analysis of the results in terms of the π electrons alone is not satisfactory.
3
Content available remote

The influence of perinatal and current dioxin and PCB exposure on reproductive parameters (sex-ratio, menstrual cycle characteristics, endometriosis, semen quality, and prematurity): a review

67%
Leijs M. M., van der Linden L. M., Koppe J. G., Olie K., van Aalderen W. M. C., ten Tusscher G. W.
Biomonitoring
|
2014
|
vol. 1
|
issue 1
EN
Polychlorinated biphenyls (PCBs) and dioxins (PCDDs/Fs) are well-known endocrine disrupters. This paper strives to elucidate the data on reproductive consequences of perinatal dioxin and PCB exposure in men and women. We focused on the following end-points: sex-ratio, endometriosis, menstrual cycle characteristics, sperm quality, and prematurity. We summarize 46 papers and compare their results including effects seen after exposure to background concentrations. Seven of twelve studies showed a decrease in sex-ratio after parental dioxin or PCB exposure. In three of the seven studies, effects were seen after paternal exposure and in three after maternal exposure. In eight of the nine studies on menstrual cycle characteristics, abnormalities were associated with PCB or dioxin exposure, however the results differed. In three studies PCB and TCDD were associated with longer menstrual cycles, while three studies indicated that an increase in PCB/PCDF exposure was associated with shorter cycles. Five studies showed effects on menstrual bleeding with higher PCB or dioxin exposure. A higher rate of irregular menstrual cycles in exposed women was seen in four studies. The conflicting outcomes probably result from variability in study design, timing of exposure and endocrine disrupting properties of the measured congeners. Nine of sixteen studies detected higher PCB or dioxin exposure in women with endometriosis. However, the manner of diagnosing endometriosis and the character of the studies varied from prospective to retrospective. Five of eight studies focusing on sperm quality showed that men, with higher serum concentrations of PCBs and/or PCB congeners and/or PCDFs, had reduced sperm quality, including increased abnormal morphology and reduced motility. The exposure timeframe seemed important here. There are two studies addressing preterm birth in relation to PCBs, one mentioned a shortening of three days of gestational age, two other studies did not find a relation. Recently one study related a shorter gestational age of half a week with overall dioxin activity measured with the CALUX method in cord blood, particularly in boys. In conclusion, exposure to PCBs and dioxins has a negative effect on the reproductive systems of human populations. Although some speculations have been made, the exact mechanism of these effects and the interactions of these compounds with other endocrine disruptors are not yet known. Age at exposure and congener specific properties are probably crucial in interpreting the observed results.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.