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. C57BI/6NNia, DBA/2JNia, B6D2F1, and B6C3F1 mice and Brown Norway (BN/RijNia), Fischer (F344/NNia) and Fischer x Brown Norway hybrid (F344 x BN F1) rats were bred and maintained on study. NCTR generated data from over 60,000 individually housed animals of the seven different genotypes and both sexes, approximately half ad libitum (AL) fed, the remainder CR. Approximately half the animals were shipped to offsite NIA investigators internationally, with the majority of the remainder maintained at NCTR until they died. The collaboration supplied a choice of healthy, long-lived rodent models to investigators, while allowing for the development of some of the most definitive information on life span, food consumption, and growth characteristics in these genotypes under diverse feeding paradigms.

a b s t r a c tInhaled aerosol dose models play critical roles in medicine, the regulation of air pollutants and basic research. The models fall into several categories: traditional, computational fluid dynamical (CFD), physiologically based pharmacokinetic (PBPK), empirical, semi-empirical, and "reference". Each type of model has its strengths and weaknesses, so multiple models are commonly used for practical applications. Aerosol dose models combine information on aerosol behavior and the anatomy and physiology of exposed human and laboratory animal subjects. Similar models are used for in-vitro studies. Several notable advances have been made in aerosol dose modeling in the past 80 years. The pioneers include Walter Findeisen, who in 1935 published the first traditional model and established the structure of modern models. His model combined aerosol behavior with simplified respiratory tract structures. Ewald Weibel established morphometric techniques for the lung in 1963 that are still used to develop data for modeling today. Advances in scanning techniques have similarly contributed to the knowledge of respiratory tract structure and its use in aerosol dose modeling. Several scientists and research groups have developed and advanced traditional, CFD, and PBPK models. Current issues under study include understanding individual and species differences; examining localized particle deposition; modeling non-ideal aerosols and nanoparticle behavior; linking the regions of the respiratory tract airways from nasal-oral to alveolar; and developing sophisticated supporting software. Although a complete history of inhaled aerosol dose modeling is far too extensive to cover here, selected highlights are described in this paper.

The ability of fibroblasts to perform unscheduled DNA synthesis (a measure of excision-repair) after UV irradiation was measured radioautographically for seven species at several times after several UV fluences. Both the initial rate and the maximum incorporation of[3H]dThd increased with the life-span of the species (shrew, mouse, rat, hamster, cow, elephant, man). Unscheduled DNA synthesis was approximately proportional to the logarithm of life-span.If an animal's cells are exposed to a constant level of physical and chemical damages per unit time, they will accumulate damages at rates dependent on the efficiencies of the repair systems for the individual damage components. If the systems are inefficient, the level of damage in DNA will increase relatively rapidly, and the resulting aberrant macromolecular synthesis may lead to cellular malfunction (and the animal's death). This point of view leads to the prediction that there is correlation between the life-span of a species and its overall ability to (3), but nondividing cells such as rabbit retinal (4) or dog neuronal cells (5) were able to repair ionizing radiation breaks as well as fibroblasts. The cells from progerioid individuals were observed to be defective in the ability to rejoin DNA strand breaks (6) but normal for repair replication after UV irradiation (7).Excision of DNA damage due to UV irradiation has been measured for a number of different species (8, 9). UV radiation is a convenient model insult because its effects on cellular DNA can be well quantitated. The excision-repair of damaged UV-irradiated DNA has been analyzed by a number of different techniques (8-11), such as (a) the actual removal of cyclobutyl pyrimidine dimers (excision), (b) repair replication (the incorporation of radioactive label into parental DNA during repair), (c) unscheduled DNA synthesis (the synthesis of DNA during non-S periods of the cell), and (d) the photolysis of bromodeoxyuridine incorporated into parental DNA during repair. Although these techniques measured different parameters, they all seem to give similar estimates of excisionrepair (12, 13), and it has been shown with several of them that normal human cells (14-16) and cells from cow (17) are very efficient at dimer excision. However, dimer excision in hamster cells is barely detectable (13)

Groups of C57BL6 mice of each sex were assigned to one of 2 dietary regimens, ad libitum (AL) or dietary restriction (DR), to study effects of food restriction on body weight, survival, and neoplasia. The AL and DR groups were subdivided into a scheduled sacrifice group for examination at 6-mo intervals, and a lifetime group to provide longevity data. Necropsies and microscopic examinations were conducted on 911 animals. In the lifetime group food consumption averaged 33.6 and 34.4 g per week by AL males and AL females, respectively; the DR counterparts were given 40% less. The diet contained 4.35 kcal/g. The average lifetime body weights were 34.8, 26.8, 22.6, and 21.6 g for AL males, AL females, DR males, and DR females, respectively, and their age at 50% survival was 27.5, 26.9, 31.7, and 33.5 mo. Maximal lifespan was increased 18% in DR males and females. Lifetime incidence of tumor-bearing mice was 89% and 86% for AL males and females, versus 64% for each sex of DR mice. Dramatic reduction occurred in female DR mice in lymphoma (9% vs 29%), pituitary neoplasms (1% vs 37%), and thyroid neoplasms (0.4% vs 8%). In males, hepatocellular tumors were reduced to 1% from 10% by DR. In contrast, the incidence of histiocytic sarcoma was increased in DR females and unaffected in DR males. Tumor onset was delayed in DR animals; 87% of all neoplasms in males and 95% in females had occurred in the AL mice by 24 mo, whereas the DR animals had only 52% and 39% of their lifetime incidence, respectively, by that age. This study provided comparative AL and DR data from C57BL6 mice examined randomly at 6-mo intervals (cross-sectional group) in parallel with data from animals in similar cohort that was unsampled and allowed to succumb naturally (longevity group). Dietary restriction reduced the lifetime percentage of tumor-bearing animals and the number of tumors per animal, and delayed the age at onset of most neoplasms.

No abstract

ABSTRACr The Amazon molly, Poecilia formosa, is a small fish that grows in clones. Hence, cells from one animal may be transplanted to another without danger of rejection. Cells from thyroid and adjacent tissue were irradiated with UV light in vitro and injected into the abdominal cavity of isogeneic recipients. At appropriate UV doses and numbers of cells injected, all recipients showed exuberant thyroid proliferation. We give arguments and data indicating that the proliferation is a tumor, not a goitrogenic response. If the UV irradiation is followed, but not preceded, by photoreactivating illumination, the yield of thyroid growths is markedly decreased. Because other investigtions have shown that photoreactivation monomerizes UV-induced cyclobutylpyimiine dimers in DNA and does not affect other photoproducts, our data indicate that pyrimidine dimers in DNA can give rise to tumors. A number of physical and chemical environmental agents damage DNA in vivo. Many of these agents are carcinogenic (1-3),-and various mutagen test systems show that there is an excellent correlation between carcinogenicity and DNA damage as measured by mutagenesis (4). Nevertheless, because treatment of DNA with carcinogens results in the formation of many products, it has not been possible to identify particular molecular changes in DNA as initiating carcinogenic events. To make such an identification, one needs an experimental trick that will change the relative proportions of the various products and permit observation of how tumor induction depends on these proportions. UV radiation makes many types of photoproducts in DNA. One of these-cyclobutylpyrimidine dimers (pyrimidine dimers)-has been shown to have lethal and mutagenic effects in microorganisms by virtue of the fact that such dimers can be monomerized by photoreactivating (PR) enzyme plus light of wavelength >320 nm (5, 6). Because, to the best of our knowledge, enzymic photoreactivation works only on pyrimidine dimers and not on other products, our finding of a PR effect strongly implicates pyrimidine dimers as the important initial DNA damage in tumor induction.There is excellent evidence that most human skin cancer arises from solar UV radiation (7) and it is a good inference that DNA is the target molecule (8 (12), cooked spinach (6), marine fish meal (6), high-protein baby cereal (4), wheat germ (2), and iodized salt (1).Cell Isolation and Injections. Donor animals (2-3 months old, 2 cm long) were placed on ice for 5 min and then given 3-min washes in each of 2.6% sodium hypochlorite, cold 95% ethanol, and sterile fish Ringer's solution. Scales were removed and tissue was excised from along the ventral aorta. The excised region contained thyroid, muscle, and cardiac tissue (from the thyroid gland, urohyal, and heart, respectively). Tissues were pooled and homogenized in fish Ringer's solution without Ca2+ or Mg2+ and containing isoniazid (0.7 mg/ml), streptomycin (1 ,sg/ml), and penicillin (1000 units/ml). Homogenization yielded primarily small clumps of two to five ...

No abstract

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. Cardiac, renal, and central nervous system pathologies were significantly inhibited by dietary restriction (DR), as were bone degeneration, inflammation, hyperplasia, amyloid induction, and atrophy of secretory organs. Hematological disorders and tumors were among the most common problem in this strain, and they were ameliorated by DR. In males, for other neoplasms, adrenal adenomas, liver tumors, and hemangiomas combined with hemangiosarcomas were decreased by DR, variably in onset and progression. In females, DR decreased pituitary tumors, mammary tumors, and alveolar carcinomas, again variably in onset and progression.