Factors Influencing Microbial Contamination of Groundwater: A Systematic Review of Field-Scale Studies.

Pathogenic microorganisms released onto the soil from point or diffuse sources represent a public health concern. They can be transported by rainwater that infiltrates into subsoil and reach the groundwater where they can survive for a long time and contaminate drinking water sources. As part of the SCA.

Innovative Mesoporous Nanosilicas: SBR Nanocomposite for Low Environmental Impact Tread Tyre.

Silica nanoparticles with different aspect ratios (A.R.) were tested as reinforcing fillers of styrenebutadiene copolymer (s-SBR) for "green tyres," i.

Issues in the design and interpretation of chronic toxicity and carcinogenicity studies in rodents: approaches to dose selection.

For more than three decades chronic studies in rodents have been the benchmark for assessing the potential long-term toxicity, and particularly the carcinogenicity, of chemicals. With doses typically administered for about 2 years (18 months to lifetime), the rodent bioassay has been an integral component of testing protocols for food additives, pesticides, pharmaceuticals, industrial chemicals, and all manner of byproducts and environmental contaminants. Over time, the data from these studies have been used to address an increasing diversity of questions related to the assessment of human health risks, adding complexity to study design and interpretation.

Influence of the silane modifiers on the surface thermodynamic characteristics and dispersion of the silica into elastomer compounds.

A good dispersion of silica into elastomers, typically used in tire tread production, is obtained by grafting of the silica with multifunctional organosilanes. In this study, the influence of the chemical structure of a triethoxysilane (TES), octadecyltriethoxysilane (ODTES), and ODTES/bistriethoxysilylpropyltetrasulfane (TESPT) mixture was investigated by inverse gas chromatography (IGC) at infinite dilution. Thermodynamic results indicate a higher polarity of the silica surface modified with TES as compared to that of the unmodified silica due to new OH groups deriving from the hydrolysis of ethoxy groups of the silane; the long hydrocarbon substituent of the ODTES lies on the surface of silica and reduces the dispersive component of the silica surface tension.

Self-organization of polystyrenes into ordered microstructured films and their replication by soft lithography.

We report on the formation of ordered arrays of micrometric holes on the surface of polystyrene (PS) films cast from volatile solvents in the presence of humidity at different temperatures. The formation mechanism is investigated for PS having different molecular weights, polydispersities, and carboxylic terminations. Among the chosen materials, a highly regular honeycomb microstructured morphology is obtained on the surface of films prepared with dicarboxy-terminated PS with = 100,000.

The effects of different levels of dietary restriction on non-neoplastic diseases in male Sprague-Dawley rats.

Background And Aims: The primary purpose of the present study was to investigate the effects of 10, 25, and 40% dietary restriction (DR) on non-neoplastic diseases in rodents at 58 and 110 weeks of age, and to determine whether low-level DR (10 and 25%) can increase the survival rate and decrease variability in chronic bioassay studies.

Methods: Male Sprague-Dawley (SD) rats (NCTR colony) were divided into four nutritional groups, consisting of an ad libitum (AL) group with unlimited access to the NIH-31 diet, and three dietary restricted (DR) groups given the NIH-31 diet reduced in amount by 10, 25, and 40%.

Results: At 110 weeks of age, the incidence of cardiomyopathy was 95, 75, 45, and 15% for AL and 10, 25, and 40% DR rats, respectively; the incidence of nephropathy was 55, 20, 15, and 0% for AL and 10, 25, and 40% DR rats, respectively.

Risk-assessment implications of mechanistic model's prediction of low-dose nonlinearity of liver tumor risk for mice fed fumonisin b(1).

A two-stage, clonal-expansion model of liver tumor risk in mice was developed by Kodell et al. (Food Addit Contam 18:237-253, 2001) based on the hypothesis that fumonisin B(1), a naturally occurring mycotoxin in corn, is not genotoxic, but rather causes cancer through the disruption of sphingolipid metabolism. This disruption is assumed to cause an increase in apoptosis, in response to which cells proliferate to compensate for reduced tissue mass.

Assessment and significance of 24-h energy intake patterns among young and aged non-affluent southern US women.

Energy intake patterns that may impact health status among non-affluent southern U.S. women from small urban communities have not been evaluated extensively.

Survival characteristics and age-adjusted disease incidences in C57BL/6 mice fed a commonly used cereal-based diet modulated by dietary restriction.

Studies of C57BL/6 mice are often restricted to one sex, with limited characterization of pathology as a function of age. As part of the National Institute on Aging/National Center for Toxicological Research Collaboration on Biomarkers, over 3000 males and 1500 females of this strain were raised, maintained, and used to evaluate longevity under specific pathogen-free conditions. A diet commonly used in testing the impact of agents was fed ad libitum or was restricted to 60% of normal consumption, starting when the mice were 14-16 weeks of age.

Caloric restriction mimetics: physical activity and body composition changes.

As the only paradigm that has consistently increased life span and inhibited the onset and/or progression of disease, dietary restriction has multiple effects on a variety of organ systems. In this brief review, the goal of the panel was to attempt to understand the role of changes in physical activity and body composition as possible modulators of the life span in experimental animals and humans. We focus on whether changes in exercise behavior and body composition produce similar changes as those found in dietary restriction and whether these changes can be used to either replace or enhance the beneficial effects of dietary restriction.

A mechanistic approach to modelling the risk of liver tumours in mice exposed to fumonisin B1 in the diet.

Data from the National Toxicology Program's carcinogenesis study of fumonisin B1 in B6C3F1 mice, conducted at the National Center for Toxicological Research, were used to fit the Moolgavkar-Venzon-Knudson (MVK) two-stage, clonal-expansion model of carcinogenesis. In addition to tumour data from the conventional 2-year bioassay, the study included data on tissue weights, cell proliferation, cell death, and sphingolipid metabolism in primary target organs. The model was used to predict 2-year liver tumour rates in female and male mice based on differences among dose groups in the effect of fumonisin B1 on the growth of normal tissue and on the proliferation of preneoplastic cells as a compensatory response to sphinganine-induced cell death.

Does caloric restriction induce hormesis?

The question of whether caloric restriction (CR) is hormetic is addressed in terms of two common definitions of the term. In terms of the older definition, i.e.

Normal mouse and rat strains as models for age-related cataract and the effect of caloric restriction on its development.

The purpose of this study was to determine: (1) which of the commonly used strains of laboratory rats and mice provide good models for human age-related cataract, and (2) whether long term caloric restriction, a regimen that prolongs both median and maximum life span in rodents, would also delay the time of appearance of this age-related pathology. Three strains of mice and two rat strains commonly used in laboratory work and maintained on either ad libitum (AL) or calorically restricted (CR) diets in the National Institutes of Aging and Diet Restriction colony were examined by slit lamp for age-related cataracts at four or more time points during their life spans. These strains were Brown Norway and Fischer 344 rats, and C57BL/6, (C57BL6 x DBA/2)F1 and (C57BL/6 x C3H)F1 mice.

Adaptive role of caloric intake on the degenerative disease processes.

Carcinogenicity and aging are characterized by a set of complex endpoints, which appear as a series of molecular events. Many of these events can be modified by caloric intake. Since most of these processes determine an organism's ability to cope with various environmental stressors, it is not surprising that a relationship (in the presence of a constant nutrient density) exists between caloric intake and time-to-tumor and/or life span.

Growth curves and survival characteristics of the animals used in the Biomarkers of Aging Program.

The collaborative Interagency Agreement between the National Center for Toxicological Research (NCTR) and the National Institute on Aging (NIA) was aimed at identifying and validating a panel of biomarkers of aging in rodents in order to rapidly test the efficacy and safety of interventions designed to slow aging. Another aim was to provide a basis for developing biomarkers of aging in humans, using the assumption that biomarkers that were useful across different genotypes and species were sensitive to fundamental processes that would extrapolate to humans. Caloric restriction (CR), the only intervention that consistently extends both mean and maximal life span in a variety of species, was used to provide a model with extended life span.

Hormesis--implications for risk assessment caloric intake (body weight) as an exemplar.

Hormesis can be considered as a parameter which has a non-monotonic relationship with some endpoint. Since caloric intake is such a parameter, and the impact of this parameter on risk assessment has been fairly well characterized, it can provide clues as to how to integrate the information from a hormetic parameter into risk assessments for toxicants. Based on the work with caloric intake, one could: (a) define a biomarker for hormetic effect; (b) integrate specific information on when in the animals lifespan the parameter is active to influence parameters such as survival; (c) evaluate component effects of the overall hormetic response; and (d) address the consequences of a non-monotonic relationship between the hormetic parameter and endpoints critical for risk assessment.

Upregulation of apoptosis with dietary restriction: implications for carcinogenesis and aging.

The maintenance of cell number homeostasis in normal tissues reflects a highly regulated balance between the rates of cell proliferation and cell death. Under pathologic conditions such as exposure to cytotoxic, genotoxic, or nongenotoxic agents, an imbalance in these rates may indicate subsequent risk of carcinogenesis. Apoptotic cell death, as opposed to necrotic cell death, provides a protective mechanism by selective elimination of senescent, preneoplastic, or superfluous cells that could negatively affect normal function and/or promote cell transformation.

Evolution and dietary restriction.

Placing lifespan in the context of the life history of an organism, Alex Comfort's work has stimulated the analysis of dietary restriction (DR) and its effects on lifespan in an evolutionary context. DR results in the curtailment of energy-intensive nonfood-gathering activities, increased efficiency of food utilization, an increase in food acquisition activity, an increase in the reproductive lifespan, and an increase in the protection of genomic integrity. These result in further refinement of the Adaptive-Longevity Related Process Theory of the effects of dietary modulation to include increased protection of the genomic integrity of cells that result from delayed reproduction, and increased ability to compete for available food.

Dietary restrictions and cancer.

Dietary restriction (DR) alters a significant environmental factor in carcinogenesis, dietary intake, thus inhibiting both spontaneous and induced tumorigenesis. Potential mechanisms for the inhibition of spontaneous cancer may include the effects of DR to do the following: decrease body weight, which decreases cellular proliferation and increases apoptosis in a number of organs that increase and decrease with body size; decrease body temperature, thereby lowering the amount of endogenous DNA damage temperature generates; decrease oxidative damage, by increasing antioxidant damage defense systems; decrease, generally, cellular proliferation; and protect the fidelity of the genome by decreasing DNA damage, increasing DNA repair, and preventing aberrant gene expression. Potential mechanisms for reducing induced tumor incidence include lowering agent activation, changing agent disposition, decreasing the adducts most associated with agent toxicity, and inhibiting tumor progression through mechanisms similar to those that can effect spontaneous tumorigenesis.

Age and temperature related changes in behavioral and physiological performance in the Peromyscus leucopus mouse.

Age-related and ambient temperature-related changes in motor activity, body temperature, body weight (b.w.), and food consumption were studied in the long-lived Peromyscus leucopus mouse at environmental temperatures of 29 and 21 degrees C.

Oral squamous cell carcinoma in ad libitum-fed and food-restricted Brown-Norway rats.

A high incidence of oral squamous cell carcinoma was present in male and female Brown-Norway rats fed ad libitum or food-restricted dietary formulations. One hundred eight-nine rats were examined from 4 dietary treatment groups: male ad libitum, male food-restricted, female ad libitum, and female food-restricted. The ad libitum treatment groups for both males and females had significantly more cases of oral squamous cell carcinoma than cohort food-restricted groups.

The physiologic, neurologic, and behavioral effects of caloric restriction related to aging, disease, and environmental factors.

Little is known about the mechanisms by which acute and chronic caloric restriction (CR) modulate disease, longevity, and toxicity. To study these endpoints, behavioral parameters such as food and water consumption and physiologic parameters such as motor activity, body temperature, metabolic output (oxygen use), and respiratory quotient (RQ) were continuously monitored in 26-month-old male B6C3F1 mice and Fischer 344 rats fed either ad libitum (AL) or a CR diet (60% of AL). Different dietary regimens were used: rodents were (1) chronically food-restricted using daily feeding starting at 14 months of age, (2) chronically food-restricted using alternate day feeding, or (3) abruptly switched from CR to AL (acute CR).

Effect of food restriction on life span and immune functions in long-lived Fischer-344 x Brown Norway F1 rats.

Life-long food restriction is known to slow aging and reduce the rate of occurrence of age-associated disease processes, but the mechanism by which this is accomplished is unknown. In this study we have examined the effect of food restriction on the proliferative response of spleen cells to mitogens and lymphokine production in 6-, 18-, and 30-month-old AL and FR Fischer-344 x Brown Norway (F-344 x BNF1) female rats whose average life span is 137 weeks on an ad libitum (AL) diet and 177 weeks on a food-restricted (FR) diet. In addition, the ability of food restriction to recall antigens was tested in 10-month-old rats by immunizing them with keyhole limpet and hen's egg albumin and measuring proliferative response of draining lymph node cells to these antigens.