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Many Chemicals (many + chemical)

Distribution by Scientific Domains

Medical Sciences	66%

Selected Abstracts

Developmental toxicity of estrogenic chemicals on rodents and other species

CONGENITAL ANOMALIES, Issue 2 2002
Taisen Iguchi
ABSTRACT, Antenatal sex-hormone exposure induces lesions in mouse reproductive organs, which are similar to those in humans exposed in utero to a synthetic estrogen, diethylstilbestrol. The developing organisms including rodents, fish and amphibians are particularly sensitive to exposure to estrogenic chemicals during a critical window. Exposure to estrogens during the critical period induces long-term changes in reproductive as well as non-reproductive organs, including persistent molecular alterations. The antenatal mouse model can be utilized as an indicator of possible long-term consequences of exposure to exogenous estrogenic compounds including possible environmental endocrine disrupters. Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans, some of which exhibit estrogenic activity by binding to the estrogen receptors. Estrogen responsive genes, therefore, need to be identified to understand the molecular basis of estrogenic actions. In order to understand molecular mechanisms of estrogenic chemicals on developing organisms, we are identifying estrogen responsive genes using cDNA microarray, quantitative RT-PCR, and differential display methods, and genes related to the estrogen-independent vaginal changes in mice induced by estrogens during the critical window. In this review, discussion of our own findings related to endocrine distuptor issue will be provided. [source]

Lactic Acid Chemical Peels as a New Therapeutic Modality in Melasma in Comparison to Jessner's Solution Chemical Peels

DERMATOLOGIC SURGERY, Issue 12 2006
KHALIFA E. SHARQUIE MBCHB
BACKGROUND Many chemicals have been used in the skin peeling for melasma such as Jessner's solution and glycolic acid. Lactic acid is an ,-hydroxy acid that has not been used before in chemical peeling of melasma. OBJECTIVE The purpose of the present work was to evaluate the efficacy and safety of lactic acid in chemical peeling of melasma in comparison to Jessner's solution chemical peels. METHODS This study was conducted at the Department of Dermatology and Venereology, Baghdad Hospital, in the period between April 2001 and August 2002. Thirty patients with melasma were included in this study. They were mostly of skin type IV according to Fitzpatrick's classification, 26 (86.67%) were women, and 4 (13.33%) were men, with an age range from 18 and 50 years (mean±SD, 33.53±6.96 years). Full clinical examination was done to all patients including Wood's light. The severity of melasma was assessed by MASI (Melasma Area Severity Index). Pure lactic acid full strength (92%, pH 3.5) was used as a new peeling agent on the left side of the face while Jessner's solution was applied to the right side of the face. The chemical peeling sessions were done every 3 weeks until the desired response was achieved. Follow-up was carried out for 6 months after the last session. RESULTS Six patients were defaulted from the study after the first session for unknown reasons. Twenty-four patients completed the study. Twenty (83.33%) were women and four were men (16.67%). Wood's light examination showed increased contrast in all patients of mostly epidermal melasma. The number of sessions ranged from 2 to 5. All patients showed marked improvement as calculated by MASI score before and after treatment, and the response was highly statistically significant. No side effect was recorded in all treated patients. CONCLUSION Lactic acid was found to be an effective and safe peeling agent in the treatment of melasma, and it was as effective as Jessner's solution. [source]

Quantitative Structure,Activity Relationship Study on Fish Toxicity of Substituted Benzenes

MOLECULAR INFORMATICS, Issue 8 2008
Zhiguo Gong
Abstract Many chemicals cause latent harm, such as erratic diseases and change of climate, and therefore it is necessary to evaluate environmentally safe levels of dangerous chemicals. Quantitative Structure,Toxicity Relationship (QSTR) analysis has become an indispensable tool in ecotoxicological risk assessments. Our paper used QSTR to deal with the modeling of the acute toxicity of 92 substituted benzenes. The molecular descriptors representing the structural features of the compounds were calculated by CODESSA program. Heuristic Method (HM) and Radial Basis Function Neural Networks (RBFNNs) were utilized to construct the linear and the nonlinear QSTR models, respectively. The predictive results were in agreement with the experimental values. The optimal QSTR model which was established based on RBFNNs gave a correlation coefficient (R2) of 0.893, 0.876, 0.889 and Root-Mean-Square Error (RMSE) of 0.220, 0.205, 0.218 for the training set, the test set, and the whole set, respectively. RBFNNs proved to be a very good method to assess acute aquatic toxicity of these compounds, and more importantly, the RBFNNs model established in this paper has fewer descriptors and better results than other models reported in previous literatures. The current model allows a more transparent chemical interpretation of the acute toxicity in terms of intermolecular interactions. [source]

Strong Static Magnetic Field Stimulates Bone Formation to a Definite Orientation In Vitro and In Vivo,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2002
Hiroko Kotani Ph.D.
Abstract The induction of bone formation to an intentional orientation is a potentially viable clinical treatment for bone disorders. Among the many chemical and physical factors, a static magnetic field (SMF) of tesla order can regulate the shapes of blood cells and matrix fibers. This study investigated the effects of a strong SMF (8 T) on bone formation in both in vivo and in vitro systems. After 60 h of exposure to the SMF, cultured mouse osteoblastic MC3T3-E1 cells were transformed to rodlike shapes and were orientated in the direction parallel to the magnetic field. Although this strong SMF exposure did not affect cell proliferation, it up-regulated cell differentiation and matrix synthesis as determined by ALP and alizarin red stainings, respectively. The SMF also stimulated ectopic bone formation in and around subcutaneously implanted bone morphogenetic protein (BMP) 2-containing pellets in mice, in which the orientation of bone formation was parallel to the magnetic field. It is concluded that a strong SMF has the potency not only to stimulate bone formation, but also to regulate its orientation in both in vitro and in vivo models. This is the first study to show the regulation of the orientation of adherent cells by a magnetic field. We propose that the combination of a strong SMF and a potent osteogenic agent such as BMP possibly may lead to an effective treatment of bone fractures and defects. [source]

Human exposure to endocrine disrupters: Standardisation of a marker of estrogenic exposure in adipose tissue,

APMIS, Issue 3 2001
Ana Rivas
In many epidemiological studies based on the direct measurement of exposure to organochlorines, the chemicals of concern are determined directly from adipose tissue samples. Although the measurement of all possible organochlorines, their metabolites, isomers and congeners may be desirable, it is expensive and time-consuming and many chemicals with hormonal activity may not yet have been identified. Testing systems are therefore required to screen for estrogenicity and to identify appropriate biomarkers of human exposure. To address this issue, we developed and standardised a method to assess the total estrogenic xenobiotic burden in human adipose tissue. The method extracts and separates the more lipophilic xenoestrogens from ovarian estrogens, with a subsequent bioassay determination of the cumulative effect of the xenoestrogens. It was applied to 400 women, using 200 mg of adipose tissue: 65% of samples showed measurable estrogenicity in the fraction where most non-polar xenoestrogens eluted, and 76% of fractions where ovarian estrogens eluted were positive for estrogenicity. Residues of 16 organochlorine pesticides were determined. No correlation was found between pesticide content and estrogenicity of the samples. The high percentage of positive samples suggests that the method is sensitive enough to be used as a biomarker of human exposure to estrogenic xenobiotics and can be applied in epidemiological studies. [source]

Oestradiol Protects Against the Harmful Effects of Fluoride More by Increasing Thiol Group Levels than Scavenging Hydroxyl Radicals

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 6 2009
Anna Dlugosz
Interactions between xenobiotics and oestrogens need to be investigated, especially as many chemicals interact with the oestrogen receptor. It is still unknown whether free radical-generating xenobiotics can influence the antioxidative ability of oestradiol (E2). In an in vitro examination of human placental mitochondria, thiobarbituric active reagent species (TBARS), hydroxyl radical (,OH) generation and protein thiol (,SH) groups were detected. 17,-E2 was examined in physiological (0.15,0.73 nM) and experimental (1,10 µM) concentrations and sodium fluoride (NaF) in concentrations of 6,24 µM. E2 in all the concentrations significantly decreased lipid peroxidation measured as the TBARS level, in contrast to NaF, which increased lipid peroxidation. Lipid peroxidation induced by NaF was decreased by E2. The influence of E2 on ,OH generation was not very significant and depended on the E2 concentration. The main mechanism of E2 protection in NaF exposure appeared to be connected with the influence of E2 on thiol group levels, not ,OH scavenging ability. The E2 in concentrations 0.44,0.73 nM and 1,10 µM significantly increased the levels of ,SH groups, in contrast to NaF, which significantly decreased them. E2 at every concentration reversed the harmful effects of NaF on ,SH group levels. No unfavourable interactions in the influence of E2 and NaF on TBARS production, ,OH generation, or ,SH group levels were observed. The results suggest that postmenopausal women could be more sensitive to NaF-initiated oxidative stress. [source]