RESUMO
In order to accurately assess aggregate exposure to a fragrance material in consumers, data are needed on consumer habits and practices, as well as the concentration of the fragrance material in those products. The present study describes the development of Phase 2 Creme RIFM model by expanding the previously developed Phase 1 model to include an additional six product types. Using subject-matching algorithms, the subjects in the Phase 1 Creme RIFM database were paired with subjects in the SUPERB and BodyCare surveys based on age and gender. Consumption of the additional products was simulated to create a seven day diary allowing full data integration in a consistent format. The inhalation route was also included for air care and other products where a fraction of product used is inhaled, derived from the RIFM 2-box model. The expansion of the Phase 1 Creme RIFM model has resulted in a more extensive and refined model, which covers a broader range of product categories and now, includes all relevant routes of exposure. An evaluation of the performance of the model has been carried out in an accompanying publication to this one.
Assuntos
Algoritmos , Cosméticos , Hábitos , Adulto , Aerossóis , Qualidade de Produtos para o Consumidor , Cosméticos/química , Feminino , Preparações para Cabelo/química , Humanos , Exposição por Inalação , Masculino , Análise por Pareamento , Pessoa de Meia-Idade , Perfumes/química , Sabões/químicaRESUMO
As part of a joint project between the Research Institute for Fragrance Materials (RIFM) and Creme Global, a Monte Carlo model (here named the Creme RIFM model) has been developed to estimate consumer exposure to ingredients in personal care products. Details of the model produced in Phase 1 of the project have already been published. Further data on habits and practises have been collected which enable the model to estimate consumer exposure from dermal, oral and inhalation routes for 25 product types. . In addition, more accurate concentration data have been obtained which allow levels of fragrance ingredients in these product types to be modelled. Described is the use of this expanded model to estimate aggregate systemic exposure for eight fragrance ingredients. Results are shown for simulated systemic exposure (expressed as µg/kg bw/day) for each fragrance ingredient in each product type, along with simulated aggregate exposure. Highest fragrance exposure generally occurred from use of body lotions, body sprays and hydroalcoholic products. For the fragrances investigated, aggregate exposure calculated using this model was 11.5-25 fold lower than that calculated using deterministic methodology. The Creme RIFM model offers a very comprehensive and powerful tool for estimating aggregate exposure to fragrance ingredients.
Assuntos
Ar/análise , Cosméticos/química , Administração Cutânea , Exposição Ambiental , Modelos Teóricos , Método de Monte Carlo , Perfumes/químicaRESUMO
Exposure of fragrance ingredients in cosmetics and personal care products to the population can be determined by way of a detailed and robust survey. The frequency and combinations of products used at specific times during the day will allow the estimation of aggregate exposure for an individual consumer, and to the sample population. In the present study, habits and practices of personal care and cosmetic products have been obtained from market research data for 36,446 subjects across European countries and the United States in order to determine the exposure to fragrance ingredients. Each subject logged their product uses, time of day and body application sites in an online diary for seven consecutive days. The survey data did not contain information on the amount of product used per occasion or body measurements, such as weight and skin surface area. Nevertheless, this was found from the literature where the likely amount of product used per occasion or body measurement could be probabilistically chosen from distributions of data based on subject demographics. The daily aggregate applied consumer product exposure was estimated based on each subject's frequency of product use, and Monte Carlo simulations of their likely product amount per use and body measurements. Statistical analyses of the habits and practices and consumer product exposure are presented, which show the robustness of the data and the ability to estimate aggregate consumer product exposure. Consequently, the data and modelling methods presented show potential as a means of performing ingredient safety assessments for personal care and cosmetics products.
Assuntos
Cosméticos , Exposição Ambiental , Modelos Teóricos , Perfumes , Adolescente , Adulto , Idoso , Qualidade de Produtos para o Consumidor , Bases de Dados Factuais , Europa (Continente) , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estados Unidos , Adulto JovemRESUMO
Ensuring the toxicological safety of fragrance ingredients used in personal care and cosmetic products is essential in product development and design, as well as in the regulatory compliance of the products. This requires an accurate estimation of consumer exposure which, in turn, requires an understanding of consumer habits and use of products. Where ingredients are used in multiple product types, it is important to take account of aggregate exposure in consumers using these products. This publication investigates the use of a newly developed probabilistic model, the Creme RIFM model, to estimate aggregate exposure to fragrance ingredients using the example of 2-phenylethanol (PEA). The output shown demonstrates the utility of the model in determining systemic and dermal exposure to fragrances from individual products, and aggregate exposure. The model provides valuable information not only for risk assessment, but also for risk management. It should be noted that data on the concentrations of PEA in products used in this article were obtained from limited sources and not the standard, industry wide surveys typically employed by the fragrance industry and are thus presented here to illustrate the output and utility of the newly developed model. They should not be considered an accurate representation of actual exposure to PEA.
Assuntos
Cosméticos , Exposição Ambiental/análise , Modelos Teóricos , Perfumes , Adulto , Qualidade de Produtos para o Consumidor , Europa (Continente) , Humanos , Álcool Feniletílico , Estados UnidosRESUMO
BACKGROUND AND OBJECTIVES: Children perinatally exposed to hepatitis C virus (HCV) should be screened for infection, yet testing rates are low. Clinical perinatal HCV testing recommendations vary and may contribute to poor completion. This study examines pediatric care factors associated with perinatal HCV testing completion. METHODS: A cohort of people living with HCV in Philadelphia, Pennsylvania, who delivered a live birth in 2016 to 2020 and their children were followed by the Philadelphia Department of Public Health. The association of completion of HCV screening with pregnant/postpartum person demographics, pediatric care factors, and testing policy were retrospectively explored. χ2 and multivariable logistic regressions were used. RESULTS: HCV-positive pregnant people gave birth to 457 children of whom 307 (67.2%) were tested for HCV according to recommendations and 79 (17.2%) were inadequately tested. Children were more likely to be tested if born to a pregnant person with HIV coinfection (P = .007), if they were always on schedule for vaccinations (P < .001), and if they attended the 18-month well visit (P < .001). Completion rates varied significantly by pediatrician's testing policy: 90.9% tested if the policy was for 2 months, 79.6% if 2 to 12 months, 61.9% if 12 months, and 58.5% if 18 months of age (P < .001). CONCLUSIONS: Timing of perinatal HCV testing policies was significantly associated with testing completion rates. Testing at 2 months was associated with far better HCV testing completion than other strategies, regardless of birthing person and pediatrician factors. These findings suggest routine HCV testing of children perinatally exposed to HCV is best achieved in the first year of life.
Assuntos
Hepatite C , Transmissão Vertical de Doenças Infecciosas , Complicações Infecciosas na Gravidez , Humanos , Feminino , Gravidez , Complicações Infecciosas na Gravidez/diagnóstico , Complicações Infecciosas na Gravidez/epidemiologia , Transmissão Vertical de Doenças Infecciosas/prevenção & controle , Hepatite C/diagnóstico , Hepatite C/epidemiologia , Estudos Retrospectivos , Philadelphia/epidemiologia , Masculino , Lactente , Recém-Nascido , Programas de Rastreamento , Adulto , Pré-EscolarRESUMO
OBJECTIVE: The objective of this study was to describe the capture-recapture method used by the Philadelphia Department of Public Health to enhance surveillance of perinatal hepatitis B virus (HBV), report on results and limitations of the process, and determine why some HBV-positive mother-infant pairs were not initially identified by Philadelphia's Perinatal Hepatitis B Prevention Program (PHBPP). METHODS: We performed capture-recapture retrospectively for births in 2008 and 2009 in Philadelphia and prospectively for births from 2010 to 2014 by independently matching annual birth certificate data to PHBPP and HBV surveillance data. We compared the number of HBV-positive mother-infant pairs identified each year to the point estimates and lower-limit estimates calculated by the Centers for Disease Control and Prevention for the Philadelphia PHBPP. RESULTS: Of 156 605 pregnancy outcomes identified between 2008 and 2014, we found 1549 HBV-positive mother-infant pairs. Of 705 pairs that were initially determined, 358 (50.7%) were confirmed to be previously unidentified HBV-positive pairs. Reasons for failing to identify these mother-infant pairs prior to capture-recapture included internal administrative issues (n = 191, 53.4%), HBV testing and reporting issues (n = 92, 25.7%), and being lost to follow-up (n = 75, 20.9%). Each year that capture-recapture was used, the number of pairs identified by the Philadelphia PHBPP exceeded the Centers for Disease Control and Prevention's lower-limit estimates for HBV-positive mother-infant pairs. CONCLUSIONS: Capture-recapture was useful for identifying HBV-positive pregnant women for Philadelphia's PHBPP and for highlighting inadequacies in health department protocols and HBV testing during pregnancy. Other health departments with access to similar data sources and staff members with the necessary technical skills can adapt this method.
Assuntos
Coleta de Dados/métodos , Hepatite B/epidemiologia , Armazenamento e Recuperação da Informação , Assistência Perinatal , Vigilância da População , Melhoria de Qualidade , Feminino , Vírus da Hepatite B/isolamento & purificação , Humanos , Transmissão Vertical de Doenças Infecciosas/prevenção & controle , Philadelphia/epidemiologia , Gravidez , Estudos RetrospectivosRESUMO
We report alkaline elution experiments that reveal the temperature dependence of DNA lesions, both single-strand breaks and DNA-protein cross-links, in L1210 cells exposed to Adriamycin. DNA damage, which at 37 degrees C is equivalent to several hundred rads of ionizing radiation exposure, diminishes as the temperature of drug exposure is lowered. At all temperatures below about 15 degrees C no DNA damage is detectable in L1210 cells exposed to Adriamycin, even at relatively high doses. The low temperature inactivity is not due to a redistribution of intracellular drug since at both 37 and 0 degrees C there is a high concentration of Adriamycin in both nuclear and cytoplasmic locations. The temperature profile for DNA damage parallels the profile for cytotoxicity, i.e., at low temperature, the drug is completely inactive as a cytotoxic agent (P. Lane, P. Vichi, D. L. Bain, and T. R. Tritton, Cancer Res., 47:4038-4042, 1987). Thus, DNA breaks and cell kill appear to be correlated with one another. However, when we examined DNA lesions in nuclei isolated from L1210 cells we found that the low temperature inability to sustain Adriamycin-induced single-strand breaks or DNA-protein cross-links was absent. In nuclei, then, the drug can provoke DNA damage at low temperature, while in whole cells it cannot. Topoisomerase II, an enzyme implicated in catalyzing DNA lesions in cells exposed to intercalating agents, retains its catalytic activity both to unknot P4 DNA at 0 degrees C, and to be induced by drug to alter the release of pBR322 supercoils, so a low temperature inactivation of this enzyme cannot explain the results. We propose that intact L1210 cells have a regulatory factor which controls DNA damage, possibly through topoisomerase II, but which is lost when nuclei are isolated.
Assuntos
Dano ao DNA , Doxorrubicina/toxicidade , Temperatura , Animais , Compartimento Celular , Núcleo Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , DNA Topoisomerases Tipo II/metabolismo , Doxorrubicina/metabolismo , Técnicas In Vitro , Leucemia L1210 , Camundongos , Plasmídeos , Inibidores da Topoisomerase IIRESUMO
Crystalline NiS, CuS, CoS2, and CdS particles were actively phagocytosed by cells and potently induced morphological transformation of Syrian hamster embryo cells in a concentration-dependent fashion. In contrast, the respective amorphous metal sulfide particles (amorphous NiS, CuS, CoS, and CdS) were not as actively phagocytosed by cultured cells and, in comparison to the crystalline form of these compounds, induced considerably less morphological transformation at both cytotoxic and noncytotoxic exposure levels. Chemical reduction of positively charged amorphous NiS with LiAlH4 resulted in active phagocytosis of these particles which was also associated with enhancement of cellular transformation. Crystalline but not amorphous NiS caused considerable strand breaks in the DNA of Chinese hamster ovary cells following 2 to 3 hr exposure at 10 micrograms/ml as determined by alkaline sucrose gradient techniques with subsequent determination of DNA molecular weight. Phagocytized inert particles such as latex beads did not induce transformation or DNA damage, suggesting that genotoxic dissolution products such as Ni2+ rather than the phagocytized particles are responsible for the observed DNA damage and cellular transformation. NiCl2 was about one-third to one-half as potent in inducing cellular transformation compared to crystalline NiS on a weight basis. These results correlate the selective phagocytosis of crystalline metal sulfides to their more potent activity in the induction of cellular transformation.
Assuntos
Compostos de Cádmio , Transformação Celular Neoplásica , DNA , Níquel , Fagocitose , Sulfetos , Animais , Cádmio , Células Cultivadas , Cobalto , Cricetinae , Cricetulus , Cristalização , Látex , Mesocricetus , MicroesferasRESUMO
Experiments were designed to measure the effect of folic acid deficiency on a major determinant of cancer lethality, the propensity to form metastases. Murine B16 melanoma cells (F10 strain) were grown in folate-deficient and -supplemented media. After 3 days, cells in the deficient medium had restricted proliferative capacity, low folate levels by bioassay, increased cell volume, abnormal deoxyuridine suppression tests, accumulation of cells in S phase by flow cytometry, and increased numbers of DNA strand breaks. These folate-deficient cells consistently initiated more pulmonary metastases than control cells when injected into host mice. Cell size did not appear to be a major factor in pulmonary metastasis formation. In vitro growth rates and cloning efficiencies were comparable for cells in both types of medium as was subcutaneous growth of tumors. We conclude that folate deficiency increases the metastatic potential of cultured melanoma cells.
Assuntos
Deficiência de Ácido Fólico/patologia , Metástase Neoplásica/patologia , Animais , Ciclo Celular , Aberrações Cromossômicas , DNA/biossíntese , Dano ao DNA , Melanoma Experimental/patologia , CamundongosRESUMO
1. The pulmonary and systemic circulatory responses to dopamine infused at 8, 15, 25 and 30 mug/kg per min were studied in eight mongrel dogs.2. Mean pulmonary artery pressure, mean left atrial pressure, mean aortic pressure, mean aortic flow and the electrocardiogram were monitored in openchest preparations. Pulmonary vascular resistance, systemic vascular resistance and stroke volume were calculated.3. Significant increases in mean pulmonary and aortic pressures were noted at dopamine infusions of 25 and 30 mug/kg per min. The left atrial pressure fell significantly at 15 mug/kg per min and rose significantly at 30 mug/kg per min. Mean aortic flow increased at all four doses, while heart rate showed no change. Pulmonary vascular resistance did not change significantly at any dose level, but systemic vascular resistance fell slightly at 8 and 15 mug/kg per min and rose significantly at 30 mug/kg per min. Stroke volume was significantly elevated at infusions of 25 and 30 mug/kg per min.4. The systemic circulatory response to dopamine is similar to that described by previous investigators.5. The increased pulmonary pressures without change in resistance suggest a dopamine-induced increase in smooth muscle tension in the pulmonary vasculature.
Assuntos
Circulação Sanguínea/efeitos dos fármacos , Dopamina/farmacologia , Circulação Pulmonar/efeitos dos fármacos , Animais , Aorta/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Cães , Dopamina/administração & dosagem , Eletrocardiografia , Músculo Liso/efeitos dos fármacos , Resistência Vascular/efeitos dos fármacosRESUMO
Both NiCl2 and crystalline alphaNiS induced DNA strand breaks in cultured Chinese hamster ovary (CHO) cells. Alkaline sucrose gradient analysis of [3H]thymidine radiolabelled DNA isolated from cells exposed to NiCl2 at 1 microgram/ml for only 2 h indicated a high degree of DNA strand breakage. Similarly crystalline alphaNiS caused substantial strand breakage at 1 microgram/ml following a 24-h treatment interval. These nickel compounds caused DNA strand breaks at concentrations which did not significantly impair normal cellular division. A concentration-dependent effect upon the number and average size of DNA fragments was obtained with both NiCl2 and crystalline alphaNiS. Since DNA strand breakage occurred at such low concentrations, these results suggest that nickel compounds which cause cellular transformation have highly selective and specific effects upon DNA structure.
Assuntos
DNA/metabolismo , Níquel/toxicidade , Animais , Divisão Celular , Linhagem Celular , Centrifugação com Gradiente de Concentração , Cloretos/toxicidade , Cricetinae , Cricetulus , DNA/genética , DNA de Cadeia Simples , Feminino , Ovário , Sulfetos/toxicidadeRESUMO
The induction of DNA repair was investigated in cultured Syrian hamster embryo (SHE) cells and Chinese hamster ovary (CHO) cells by cesium chloride equilibrium gradient sedimentation techniques following exposure to NiCl2, amorphous NiS, crystalline NiS and crystalline Ni3S2. Significant repair was induced in CHO cells by 1 microgram/ml of crystalline NiS following 24 h of treatment while 5 micrograms/ml caused more than twice the repair activity. In contrast amorphous NiS at 10 micrograms/ml for 24 h induced little repair in these cells. Similarly amorphous NiS did not induce repair at 5-10 micrograms/ml for 24 h in SHO cells while crystalline Ni3S2, and NiCl2 caused substantial induction of DNA repair synthesis at 10 micrograms/ml or 100 microM, respectively. These results demonstrate that nickel compounds which are potent transforming agents and induce damage to DNA also result in the induction of DNA repair. Repair synthesis was detected at concentrations of metal compounds which result in no detectable damage to DNA.
Assuntos
Reparo do DNA/efeitos dos fármacos , Replicação do DNA/efeitos dos fármacos , Níquel/farmacologia , Animais , Linhagem Celular , Cricetinae , Cricetulus , Embrião de Mamíferos , Feminino , Mesocricetus , Ovário , SolubilidadeRESUMO
OBJECTIVE: To measure the effects of case management on an older population's costs of health care. DESIGN: A 1-year randomized controlled trial. SETTING: Multiple sites of care in San Francisco, California. PARTICIPANTS: Patients aged 65 or older of primary care physicians in a large provider organization bearing financial risk for their care (n = 6409). INTERVENTION: Screening for high risk and provision of social work-based case management. OUTCOME MEASURES: Volume and cost of hospital, physician, case management, and other health-related services. RESULTS: The experimental group used more case management services than the control group (0.09 vs. 0.02 months per person, P<.001). The experimental group's average total payments for health care were slightly lower ($3148 vs $3277, P = .40). CONCLUSIONS: This study provides no statistically significant evidence that social work-oriented case management reduces the use or the cost of health care for high-risk older people. Other potentially favorable effects of this type of case management need to be evaluated, as do the effects of other types of case management.
Assuntos
Administração de Caso/economia , Custos de Cuidados de Saúde/estatística & dados numéricos , Serviços de Assistência Domiciliar/organização & administração , Medicare Part C/organização & administração , Serviço Social/organização & administração , Idoso , Administração de Caso/organização & administração , Controle de Custos , Feminino , Avaliação Geriátrica , Pesquisa sobre Serviços de Saúde , Humanos , Masculino , Avaliação das Necessidades/organização & administração , Avaliação de Programas e Projetos de Saúde , Encaminhamento e Consulta , Fatores de Risco , São Francisco , Inquéritos e Questionários , Estados UnidosRESUMO
The genotoxic potential of 2-hydroxy 4-methoxy-benzophenone (benzophenone-3, Bz-3), a commonly used sunscreen, has been evaluated previously with in vitro systems. Data from Salmonella studies (with and without activation) have been predominantly negative, but two reports have shown weakly positive results in a single bacterial strain under conditions of metabolic activation. In addition, Bz-3 has been reported to induce chromosome aberrations and equivocal results for sister chromatid exchange in Chinese hamster ovary (CHO) cells. We used the Drosophila somatic mutation and recombination test (SMART) and in vivo cytogenetics in rat bone marrow to define the potential for in vivo expression of this in vitro activity. For the SMART assay, larva from a mating of "multiple wing hair" (mwh) females with heterozygous "flare" (flr) males were exposed to 0, 3000, or 3500 ppm Bz-3 or 25 ppm dimethylnitrosamine (DMN, positive control) for 72 hr. A recombination between the mwh and flr genes produces twin wing spots, while events such as deletions produce single spots. None of the Bz-3-treated larva produced flies with significantly more single or multiple wing spots than controls. In contrast, DMN-treated larva produced flies with significantly more single or multiple wing spots than controls. The in vivo cytogenetic assay in rat bone marrow cells was conducted to evaluate the clastogenicity of Bz-3. Sprague-Dawley rats were treated by oral gavage with a single administration of 0.0, 0.5, 1.67, or 5 gm/kg Bz-3 or a single dose of 5 gm/kg/day Bz-3 for 5 consecutive days. Cyclophosphamide (CP) was the positive control and was administered at 20 mg/kg with both treatment regimens. Colchicine growth-arrested bone marrow cells were collected 8 and 12 hr after the single treatment and 12hr after the last daily treatment. Under either treatment protocol none of the Bz-3 concentrations caused any significant increase in chromosomal aberrations. Results from these two studies strongly support the conclusion that Bz-3 is not genotoxic in vivo.
Assuntos
Benzofenonas/toxicidade , Aberrações Cromossômicas , Mutagênese , Mutagênicos/toxicidade , Protetores Solares/toxicidade , Animais , Medula Óssea/efeitos dos fármacos , Células da Medula Óssea , Drosophila melanogaster/efeitos dos fármacos , Feminino , Masculino , Testes de Mutagenicidade , Ratos , Ratos Sprague-Dawley , Asas de AnimaisRESUMO
DNA plays an essential role not only in dividing cells, but also in postmitotic cells such as neurons. Accumulated damage to the nuclear DNA will result in damage to neuronal metabolism. There is suggestive evidence of altered DNA in ALS, Alzheimer's and Parkinson's diseases, and of deficiency of DNA repair mechanisms in these age-related neuronal degenerations and in Huntington's disease. We suggest that these DNA abnormalities are more likely to be the cause of the diseases, rather than an effect of the disease process.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Doenças dos Gânglios da Base/metabolismo , DNA/metabolismo , Doença de Alzheimer/metabolismo , Esclerose Lateral Amiotrófica/etiologia , Doenças dos Gânglios da Base/etiologia , Carcinógenos/metabolismo , Fenômenos Químicos , Química , Reagentes de Ligações Cruzadas/farmacologia , DNA/efeitos da radiação , Reparo do DNA , Humanos , Doença de Huntington/metabolismo , Doença de Parkinson/metabolismoRESUMO
We have previously reported reduced ability of ALS fibroblasts to repair genomic DNA damage produced by alkylating agents. This report presents our experience of studying DNA repair in lymphocytes from ALS patients. The repair of N-methylpurines produced by treatment with the alkylating agent, methyl methanesulfonate, was studied in T-lymphocytes from patients with sporadic and familial ALS, and appropriate controls. Repair of damage was quantitated by using alkaline elution for genomic DNA repair, and methoxyamine protection of abasic sites in DNA fragments for gene-specific repair in the dihydrofolate reductase (dhfr) gene, at time points 0, 6 h and 24 h. No significant repair rate differences were observed between ALS and control lymphocytes in either genomic or gene-specific DNA repair. The possible reasons for the discrepancy with our earlier results in lymphocytes and fibroblasts are discussed.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Reparo do DNA , DNA/metabolismo , Nucleotídeos de Purina/genética , Linfócitos T/metabolismo , Idoso , Sobrevivência Celular , Feminino , Humanos , Masculino , Metanossulfonato de Metila/farmacologia , Pessoa de Meia-Idade , Linfócitos T/fisiologia , Tetra-Hidrofolato Desidrogenase/genéticaRESUMO
We studied survival and DNA repair capacity in cultured sporadic ALS and control skin fibroblasts after treatment with DNA damaging agents producing different types of lesions. Mean survival in ALS and control fibroblasts was similar after exposure to ultraviolet (UV) light, x-rays and mitomycin C (MMC). Both mean survival and mean unscheduled (repair) DNA synthesis (UDS) were significantly reduced in ALS fibroblasts following treatment with the alkylating agent methyl methane sulfonate (MMS). These data suggest that ALS cells are relatively deficient in the repair of alkylation damage, possibly of apurinic/apyrimidinic sites, and that they are not unduly sensitive to DNA damage produced by UV light, x-rays and MMC. Normal survival and UDS seen in some patients' cells after MMS treatment indicate a spectrum of repair efficiency, and suggest heterogeneity of the biochemical defect in ALS.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Reparo do DNA , Adulto , Idoso , Sobrevivência Celular , Células Cultivadas , DNA/biossíntese , DNA/efeitos dos fármacos , DNA/efeitos da radiação , Reparo do DNA/efeitos da radiação , Fibroblastos/metabolismo , Fibroblastos/efeitos da radiação , Humanos , Metanossulfonato de Metila/farmacologia , Pessoa de Meia-Idade , Mitomicina , Mitomicinas/farmacologia , Raios Ultravioleta , Raios XRESUMO
HgCl2 is extremely cytotoxic to Chinese hamster ovary (CHO) cells in culture since a 1-h exposure to a 75- microM concentration of this compound reduced cell plating efficiency to 0 and cell growth was completely inhibited at 7.5 microM . The level of HgCl2 toxicity depended upon the culture incubation medium and has previously been shown to be inversely proportional to the extracellular concentration of metal chelating amino acids such as cysteine. Thus, HgCl2 toxicity in a minimal salts/glucose maintenance medium was about 10-fold greater than the toxicity in McCoy's culture medium. The HgCl2 toxicity in the latter medium was 3-fold greater than that in alpha-MEM which contains more of the metal chelating amino acids. When cells were exposed to HgCl2 there was a rapid and pronounced induction of single strand breaks in the DNA at time intervals and concentrations that paralleled the cellular toxicity. The DNA damage was shown to be true single strand breaks and not alkaline sensitive sites or double strand breaks by a variety of techniques. Consistent with the toxicity of HgCl2, the DNA damage under an equivalent exposure situation was more pronounced in the salts/glucose than in the McCoy's medium and more striking in the latter medium than in alpha-MEM. Most of the single strand breaks occurred within 1 h of exposure to the metal. We believe that the DNA damage caused by HgCl2 leads to cell death because the DNA single strand breaks are not readily repaired. DNA repair activity measured by CsCl density gradient techniques was elevated above the untreated levels at HgCl2 concentrations that produced little measurable binding of the metal to DNA or few single strand breaks assessed by the alkaline elution procedure. DNA repair activity decreased at HgCl2 concentrations that produced measurable DNA binding and single strand breaks. These irreversible interactions of HgCl2 with DNA may be responsible for its cytotoxic action in cells.
Assuntos
DNA/antagonistas & inibidores , Mercúrio/toxicidade , Animais , Linhagem Celular , Cricetinae , Meios de Cultura , Cisteína/farmacologia , Reparo do DNA/efeitos dos fármacos , DNA de Cadeia Simples , Relação Dose-Resposta a Droga , Feminino , Cinética , Cloreto de Mercúrio , OvárioRESUMO
In vitro cultures of human peripheral blood lymphocytes, both unstimulated G0 cells as well as phytohemagglutinin (PHA) stimulated cells, have been used in the investigation of DNA repair following different types of damage, including that induced by ultraviolet light, ionizing radiation, and chemical agents. We report here repair of DNA damage in cultured normal human T-lymphocytes after treatment with the alkylating agents, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or methanesulfonate (MMS), as measured by the alkaline elution technique. T-lymphocytes cultured with different sources of T-cell growth factors (TCGFs) were shown to have similar repair levels, as measured by loss of single-strand breaks. However, diminished repair was observed with in vitro culture age when T-cells were cultured with PHA and TCGF for a 3-week period. Cell-cycle analysis performed on asynchronously growing cultures indicated that differential repair with in vitro aging was not cell-cycle-related. Fluorescence Activated Cell Sorting (FACS) was used to determine the percentages of CD4+ and CD8+ T-cell subsets present during the in vitro culture periods. Cultures consisted primarily of CD4+ cells until day 20 when the percentage of CD8+ cells increased to approximately 50% of the T-cell population. Neither the absolute percentages of CD4+ and CD8+ cells not the CD4+/CD8+ ratios correlated with repair rates of cultured T-cells. Therefore, the observed decreases in the repair of alkylating agent-induced damage are not due solely to the change in the CD4+/CD8+ ratio.