Origin of inbred NZ mouse strains.

Inbreeding of mice was begun in 1948 in our labora tories in response to the request of Dr. Franz Bielschow sky, who recognized the need for genetically and nutri tionally uniform animals for cancer research. The resulting strains of inbred NZ mice proved useful for research in immunology, biochemistry, and other fields, and they have been widely distributed. We often have inquiries from investigators at other laboratories who sometimes are unaware that the original colonies of NZ strain mice are distinct from subcolonies maintained by the Medical School Breeding Station and by other de partments of the University of Otago Medical School. We hope that the information given here will enable in vestigators elsewhere to trace the relationship of their animals to the original strains. The derivation and subsequent distribution of our NZ strains of mice to other laboratories is summarized in Chart 1 and Table 1. References to publications from our laboratories on these strains are also brought together to expand and correct information available from the Standardized Nomenclature List (18). The University of Otago Medical School mouse colony was formed with randomly bred mice brought to New Zealand by Mr. W. H. Hall in 1930 from the Imperial Cancer Research Fund Laboratories at Mill Hill, Lon don. Several pairs of mice, each selected for similar coat color but having no systematic relationship, were ob tained from the Medical School colony in April 1948, and from these our main strains were developed. From their inception the NZ mouse strains have been maintained in the laboratories of the Hugh Adam Department of Can cer Research, separate from the Medical School animal colonies. Since the selection of the original ancestral pairs there have been no other introductions of mice into our colonies. NZO/BI Mice. Descendants of a pair of agouti mice were inbred by b X s mating, with fixation of the agouti coat color. From FIO increasing numbers of the mice were obese, and from F12 to F17 there was selection for this character in the propagation of the strain, which is now in the 84th generation (2a-c, e,j, I, m, 6, 7, 10, 12, 19-21). NZB/BI Mice. In the third generation (F3) descend ants from the agouti mice leading to the NZO strain, some offspring had black coats, and from 1 pair of black littermates a new line was begun. Brother X sister mat10