Tumour and blood leukocyte DNAs from sporadic breast cancer patients were examined for chromosome 1 loss of heterozygosity using a probe for a polymorphic epithelial mucin, PEM, which is expressed in greater than 92% of breast carcinomas as well as in normal lactating breast tissue. Expression is detected by the monoclonal antibodies (MAbs) HMFG-1, -2 and SM-3 which react with epitopes in the 20 amino-acid repeat unit of the core protein. The PEM probe has been mapped to the chromosome band 1q21, a region that is often incriminated in chromosomal rearrangements in breast tumours. Loss of heterozygosity or alteration at the PEM locus was detected in 34% of the 70 informative patients examined. Twenty of the 24 individuals showed loss of an allele, whereas 4 showed gain of an additional allele or amplification of an existing allele. Twenty-eight percent of informative cases exhibited alterations at the MS32 locus, 1q42-43, and 20% had alterations at the short arm locus MS1 at 1p33-35. These findings identify the long arm of chromosome 1 and in particular the region around the PEM gene for localization of a gene whose loss or alteration may, in some tumours, contribute to the progression of disease in breast cancer patients.

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Mitochondrial pellets isolated in 0.25 M sucrose from pigeon breast muscle and washed once contained 77 ± 1.43 g water per 100 g pellet, 7.8 ± 2.0 meq K and 4.29 meq Na per kg dry weight. The Na:K ratio for mitochondria was almost 5 times that of muscle, suggesting that mitochondria might contain some of the "excess" sodium of skeletal muscle. A comparison of mitochondria isolated in three different sucrose media (0.25 M, 0.45 M, 0.88 M) was made with respect to sodium, potassium, and water concentrations of unwashed mitochondria (M1) and those washed once (M2). Washing always resulted in a loss of sodium and potassium but neither repeated washing nor suspension in hypotonic solutions removed all of the cations. These findings and the high concentration ratios observed between mitochondria and the suspension media attested to the presence of "bound" or restricted cations. A few analyses for nitrogen, phosphorus, and lipid made on the various mitochondrial preparations, on microsomal-like material, and on a "floating layer" believed to be washed out of M1 preparations by resuspension, drew attention to the possibility of altering the character of the unit of reference (dry weight, mg N, etc.) used for expressing concentrations of cations. The "floating layer" was unique in being high in lipid and high in sodium. Analytical data and electron micrographs provided evidence that 0.45 M sucrose preserved the chemical and morphological integrity of the mitochondria better than the other concentrations tested.