While regulatory requirements for carcinogenicity testing of chemicals vary according to product sector and regulatory jurisdiction, the standard approach starts with a battery of genotoxicity tests (which include mutagenicity assays). If any of the in vivo genotoxicity tests are positive, a lifetime rodent cancer bioassay may be requested, but under most chemical regulations (except plant protection, biocides, pharmaceuticals), this is rare. The decision to conduct further testing based on genotoxicity test outcomes creates a regulatory gap for the identification of non-genotoxic carcinogens (NGTxC). With the objective of addressing this gap, in 2016, the Organization of Economic Cooperation and Development (OECD) established an expert group to develop an integrated approach to the testing and assessment (IATA) of NGTxC. Through that work, a definition of NGTxC in a regulatory context was agreed. Using the adverse outcome pathway (AOP) concept, various cancer models were developed, and overarching mechanisms and modes of action were identified. After further refining and structuring with respect to the common hallmarks of cancer and knowing that NGTxC act through a large variety of specific mechanisms, with cell proliferation commonly being a unifying element, it became evident that a panel of tests covering multiple biological traits will be needed to populate the IATA. Consequently, in addition to literature and database investigation, the OECD opened a call for relevant assays in 2018 to receive suggestions. Here, we report on the definition of NGTxC, on the development of the overarching NGTxC IATA, and on the development of ranking parameters to evaluate the assays. Ultimately the intent is to select the best scoring assays for integration in an NGTxC IATA to better identify carcinogens and reduce public health hazards.

Neuropeptide Y (NPY) is a peptide found in a variety of hypothalamic loci which is frequently colocalized with catecholamines. It is also secreted into hypophyseal portal vessels. The injection of NPY into the third ventricle (3V) lowered plasma GH levels in conscious, freely moving male rats. To determine the physiological significance of the hypothalamic inhibitory action of the peptide, highly specific antiserum directed against NPY was injected into the 3V of conscious rats. 3V injection of the antiserum evoked a significant elevation of plasma GH within 2 h on comparison to values in normal rabbit serum-injected, ovariectomized rats. The difference increased and reached a maximum at 6 h after injection. On the other hand, there was no effect of the antiserum in ovariectomized, estrogen, progesterone-blocked rats. Intraventricular injection of the anti-NPY serum also caused a significant elevation of plasma GH within 2 h in normal male rats and the increases above values in normal rat serum-injected control animals became even more significant at 3 and 4 h. To determine the mechanism by which NPY lowers GH after its intraventricular injection, its effect on the release of somatostatin (SRIF) from median eminence fragments incubated in vitro was examined. NPY stimulated SRIF release with a highly significant effect at a concentration of 10(-9) M. Borderline stimulation was observed at doses as low as 10(-11) M. The curve was bell-shaped with a declining release at 10(-8) M and 10(-7) M. The releasing action of NPY was blocked by either the alpha 1-receptor blocker, prazosin (10(-6) M), or the beta-receptor blocker, propranolol (10(-6) M), but was not affected by the alpha 2-receptor blocker, yohimbine (10(-6) M). We conclude that NPY has a physiologically significant inhibitory action within the hypothalamus to suppress GH release in ovariectomized female and intact male rats by stimulation of SRIF release by alpha 1 and beta-adrenergic receptor-mediated mechanisms.

Neural degeneration is one of the clinical manifestations of ataxia-telangiectasia, a disorder caused by mutations in the Atm protein kinase gene. However, neural degeneration was not detected with general purpose light microscopic methods in previous studies using several different lines of mice with disrupted Atm genes. Here, we show electron microscopic evidence of degeneration of several different types of neurons in the cerebellar cortex of 2-month-old Atm knockout mice, which is accompanied by glial activation, deterioration of neuropil structure, and both pre-and postsynaptic degeneration. These findings are similar to those in patients with ataxia-telangiectasia, indicating that Atm knockout mice are a useful model to elucidate the mechanisms underlying neurodegeneration in this condition and to develop and test strategies to palliate and prevent the disease.

Because several peptides ornally found in the pituitary as within the central nervous system have been l i in lymphoid tissues and because somatostatin (soma inrelease-inhibiting hormone, SRIH) can act on cells ofthe immune system, we searched for this peptide in lymphoid organs. We demonstrated that SRIH mRNA exists in lymphoid tissue, albeit in smaller levels than in the perive region of the hypotaus, the brain region that contains the highest level of this mRNA. SRIH mRNA was found in the spleen and thymus ofmale rats and in the spleen, thymus, and bursa of Fabricius of the chicken. Its loc ton in the bursa indices that the peptide must be present in B lymphocytes since this is the site of origin of B lymphocytes in birds. The SRII concentration in these lymphoid organs as determined by radloimmunoassay was greater in the thymus than in the spleen of the rat. These concentrations were 50 times less than those found in the periventricular region of the hypodtalmus, the site ofthe perikarya ofSRIH-containing neurons. In the chicken, as in the rat, the concentration of SRII was greater in the thymus than in the spleen; it was present in the bursa ofFabridus, also in higher concentration than in the spleen.Fluorescence immucytochemir revealed the presence of SRIH-positive cells in dusters inside the white pulp and more dispersed within the red pulp ofthe spleen of both the rat and the chicken. The thymus from these species o contained SRIHpositive cells within the medulla and around the ctcomedullary junction. In the chicken, there were large'dusters of SRIHpositive cells in the medullary portion ofeach nodule of the bursa ofFabricius. Preabsorptionoftheprimayantiseru orreplacing this antiserum with normal rabbit serum verified the specificity of aning. Sequential immunostainingof the same sections from rat spleen using first SRIH antibody and subsequently a monoclonal antibody against a rat B-cell surface antigen revealed the presence of SRIH immunoreactivity in some, but not all, B cells. Other cell types in spleen not yet identified also stained positively with the SR.II antibody but were not reactive to monoclonal antibodies to rat Thy-1.1, a marker for all the thymic T lymphocytes. The possibility that SRIH is present in other populations ofcells in the spleen cannot be ruled out. Sequential immu nin of the same sections of rat thymus revealed the presence of SRIH immunoreactivity in a small population of T lymphocytes in the medulla, as revealed by the Thy-1.1 marker. The SRIH-positive cells were nonimmunoreactive when exposed tothe B-cell marker; however, the possibility that SRIH is present in other cells was not investigated. Thus, our results indicate that SRIH is synthesized and stored in cells of the immune system. SRHI may be secreted from these cells to exert paracine actions that alter the function of immune cells in spleen and thymus.Somatostatin (somatotropin-release-inhibiting hormone, SRIH), originally described and isolated from the hypothalamus (1, 2) by its ability to inhibit growth ...