The identification of ras oncogenes in human and animal cancers including precancerous lesions indicates that these genes participate in the early stages of neoplastic development. Yet, these observations do not define the timing of ras oncogene activation in the multistep process of carcinogenesis. To ascertain the timing of ras oncogene activation, an animal model system was devised that involves the induction of mammary carcinomas in rats exposed at birth to the carcinogen nitrosomethylurea. High-resolution restriction fragment length polymorphism analysis of polymerase chain reaction-amplified ras sequences revealed the presence of both H-ras and K-ras oncogenes in normal mammary glands 2 weeks after carcinogen treatment and at least 2 months before the onset of neoplasia. These ras oncogenes can remain latent within the mammary gland until exposure to estrogens, demonstrating that activation of ras oncogenes can precede the onset of neoplasia and suggesting that normal physiological proliferative processes such as estrogen-induced mammary gland development may lead to neoplasia if the targeted cells harbor latent ras oncogenes.

We have designed an Ha-ras/thymidine kinase (TK) cassette that permits the incorporation of chemically synthesized adducts within specific domains of the rat Ha-ras protooncogene. This cassette has been used to evaluate the mutagenicity of O6-substituted guanine residues, including 06-methylguanine and 06-benzylguanine, incorporated within the 12th codon of this locus. Mutations were monitored by the ability of these modified Ha-ras DNAs to transform Rat4 TKcells. Our results indicate that both types of 06-substituted guanines are substantially mutagenic, although the methyl substituent induced a 2-fold higher percentage of transformed Rat4 TKV colonies than its bulkier benzyl analogue. Interestingly, the mutagenicity of both 0-substituted guanines was found to be independent of their relative position within codon 12, therefore suggesting that the specific activation of Ha-ras oncogenes by GGA -. GAA mutations in tumors induced by methylating carcinogens might be due to differences in the accessibility of these guanine residues to the carcinogen rather than to a differential rate of repair.

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Literature on recovery of nitrogen and phosphorous from wastewater in the form of value-added struvite fertilizer has been critically reviewed towards the evolution of a sustainable management strategy. Presence of nitrogen and phosphorus is widespread in both domestic as well as industrial wastewater streams such as swine wastewater, landfill leachate, urine waste, dairy manure, coke wastewater, and beverage wastewater. Where these nitrogen and phosphorus compounds cause eutrophication of water bodies and considered as harmful discharges to the environment, they can be turned useful through simple chemical conversion into struvite (MgNH4PO4·6H2O). In extensive studies on wastewater treatment, aspects of recovery of valuable materials remain dispersed. In the present article, almost all relevant aspects of sources of raw materials, chemistry and technology of struvite production, and its detailed characterization have been captured in a systematic and classified way so as to help in planning and designing an integrated scheme of struvite production through conversion of nitrogen and phosphorus components of waste streams. The study will help in formulating a new waste management strategy in this context by shifting focus from removal to recovery of nutrients from waste streams.