One of the distinguishing features of multiple myeloma (MM) is the proliferation of plasma cells that home to the bone marrow (BM). However, there still remains some uncertainty concerning the presence of related malignant cells in the peripheral blood of myeloma patients. Using consensus oligonucleotide primers, we amplified the third complementary determining region (CDR3) of rearranged immunoglobulin heavy chain alleles from MM marrow samples by polymerase chain reaction (PCR). From the sequences of the products, we derived allele-specific oligonucleotides (ASO), and these were used in subsequent amplification reactions to detect malignant clones in the peripheral blood of myeloma patients. This method is highly specific and sensitive to 1 malignant cell in the background of 10(5) normal cells. Using this method we detected circulating malignant cells in 13 of 14 previously untreated MM patients. Furthermore, by applying ASO-PCR to artificial titrations of initial BM DNA sample into normal peripheral blood lymphocyte (PBL) DNA we were able to generate standard curves and quantitate the amount of tumor in the patient PBL. We observed a wide variation in the amount of circulating tumor between patients. In addition, we found that the incidence of circulating tumor cells was independent of BM tumor burden and stage of disease. The detection and quantitation of circulating tumor cells in the PBL of MM patients may offer an alternative assessment of the disease and may be an important consideration in the use of peripheral stem cells in bone marrow transplantation.

Mitochondrial (mt) DNA restriction endonuclease assays of seven populations of Oncorhynchus tshawytscha from British Columbia and Alaska disclosed six distinct maternal (clonal) lines, of which three were represented by more than one individual. The three major lines were not population specific. Of the British Columbia fish sampled, 41 belong to clonal line A (82% of the 50 fish sampled in British Columbia). Clonal line C contained 10 fish from Alaskan sites only. Clonal line B contained 20 fish from both British Columbia and Alaska sites. Intraspecific mtDNA sequence divergence is low (less than 1% in ail cases) compared with other species surveys of this sort. Comparison with protein electrophoretic studies of O. tshawytscha reveals similar levels of population structuring. A database of mtDNA fragment sizes produced by the 14 restriction endonucleases is included.

The mitochondrial DNA (mtDNA) from the Townsend's vole, Microtus townsendii, was compared with mouse mtDNA by positioning vole restriction enzyme fragments on the known laboratory mouse mtDNA molecule by homology hybridization. The vole mitochondrial genome is conserved in general sequence organization and size but does contain a nonhomologous region of more than 600 base pairs not found in the mouse sequence. Thirty-five voles were collected from seven different localities throughout the range of the species, including insular populations on Bowen and Vancouver islands. The variation of vole mtDNA sequences within this species was assayed with six hexameric and four tetrameric type II restriction endonucleases. These individuals can be divided into seven distinct maternal lines. The level of nucleotide substitution between populations is shown to be as high as 0.896 ± 0.350%. The voles from Bowen Island showed no detectable variation within their population, or divergence from a mainland population on the adjacent coast. This fact suggests a recent colonization of Bowen Island. The samples from Vancouver Island fall into two major maternal lines, which show 0.453 ± 0.240% divergence. These insular maternal lines are 0.677 ± 0.257% divergent from the most closely related mainland population. These results suggest that the voles on Vancouver Island represent long-established maternal lines, and are not derived by a recent colonization from a mainland source population. Based on conservative estimates for rates of nucleotide substitution, Vancouver Island has been inhabited by the Townsend's vole since at least the Olympic interglacial.

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