The use of bromodeoxyuridine labeling in the human lymphocyte HGPRT somatic mutation assay

The autoradiographic assay developed by Strauss and Albertini (1979) to quantitate human in vivo somatic mutation at the hypoxanthine guanine phosphoribosyl-transferase locus uses tritiated thymidine to identify mutant cells by their ability to pass through 'S' phase in the presence of 6-thioguanine. An alternative method, based on the incorporation of bromodeoxyuridine (BrdUrd) into the DNA of proliferative cells, followed by differential staining with the fluorescence-plus-Giemsa method, was used to identify 3 classes of lymphocyte nuclei: (a) small darkly stained nuclei, (b) large, reddish-colored nuclei with an apparent nucleolus, and (c) large, bluish-colored nuclei. By double labeling with BrdUrd and tritiated thymidine, it was determined that only the nuclei of the third class had incorporated BrdUrd. These results demonstrate that the technique used for sister-chromatid differentiation can be used to detect putative HGPRT mutants and to determine variant frequencies at the HGPRT locus.     

Abundant alkali-sensitive sites in DNA of human and mouse sperm

The DNA of human and mouse sperm cells was analyzed by single-cell microgel electrophoresis, by agarose gel electrophoresis, and by alkaline elution--three techniques that can detect single-strand DNA breaks and/or labile sites. Under these conditions a surprisingly large number of single-strand DNA breaks, approximately 10(6) to 10(7) per genome, were detected in human and mouse sperm but not in human lymphocytes or in mouse bone marrow cells. These breaks were also present in chicken erythrocyte DNA, which is also highly condensed. These breaks were not observed under neutral pH conditions nor under denaturing conditions not involving alkali, suggesting that these sites are alkali-sensitive and do not represent preexisting single-strand breaks. The high frequency of such sites in sperm from healthy mouse and human donors suggests that they represent a functional characteristic of condensed chromatin rather than DNA damage.     

Evolutionary conservation of the chromosomal configuration and regulation of amylase genes among eight species of the Drosophila melanogaster species subgroup

Nuclear DNA was extracted from each of the eight species comprising the Drosophila melanogaster species subgroup. Southern hybridization of this DNA by using a molecular probe specific for the alpha-amylase coding region showed that the duplicated structure of the amylase locus, first found in D. melanogaster, is conserved among all species of the melanogaster subgroup. Evidence is also presented for the concerted evolution of the duplicated genes within each species. In addition, it is shown that the glucose repression of amylase gene expression, which has been extensively studied in D. melanogaster, is not confined to this species but occurs in all eight members of the species subgroup. Thus, both the duplicated gene structure and the glucose repression of Drosophila amylase gene activity are stable over extended periods of evolutionary time.      

Aneuploidy in mammalian somatic cells in vivo

Aneuploidy is an important potential source of human disease and of reproductive failure. Nevertheless, the ability of chemical agents to induce aneuploidy has been investigated only sporadically in intact (whole-animal) mammalian systems. A search of the available literature from the EMCT Aneuploidy File (for years 1970-1983) provided 112 papers that dealt with aneuploidy in mammalian somatic cells in vivo. 59 of these papers did not meet minimal criteria for analysis and were rejected from subsequent review. Of the remaining 53 papers that dealt with aneuploidy induction by chemical agents in mammalian somatic cells in vivo, only 3 (6%) contained data that were considered to be supported conclusively by adequate study designs, execution, and reporting. These 3 papers dealt with 2 chemicals, one of which, mercury, was negative for aneuploidy induction in humans, and the other, pyrimethamine, was positive in an experimental rodent study. The majority of papers (94%) were considered inconclusive for a variety of reasons. The most common reasons for calling a study inconclusive were (a) combining data on hyperploidy with those on hypoploidy and/or polyploidy, (b) an inadequate or unspecified number of animals and/or cells per animal scored per treatment group, and (c) poor data presentation such that animal-to-animal variability could not be assessed. Suggestions for protocol development are made, and the future directions of research into aneuploidy induction are discussed.     

Growth of Phytomonas serpens in a Defined Medium; Nutritional Requirements

ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.     

Membrane Skeletal Proteins and Their Integral Membrane Protein Anchors are Targets for Tyrosine and Threonine Kinases in Euglena

ABSTRACT. Proteins of the membrane skeleton of Euglena gracilis were extensively phosphorylated in vivo and in vitro after incubation with [³²P]-orthophosphate or γ-[³²P] ATP. Endogenous protein threonine/serine activity phosphorylated the major membrane skeletal proteins (articulins) and the putative integral membrane protein (IP39) anchor for articulins. The latter was also the major target for endogenous protein tyrosine kinase activity. A cytoplasmic domain of IP39 was specifically phosphorylated, and removal of this domain with papain eliminated the radiolabeled phosphoamino acids and eliminated or radically shifted the PI of the multiple isoforms of IP39. In gel kinase assays IP39 autophosphorylated and a 25 kDa protein which does not autophosphorylate was identified as a threonine/serine (casein) kinase. Plasma membranes from the membrane skeletal protein complex contained threonine/serine (casein) kinase activity, and cross-linking experiments suggested that IP39 was the likely source for this membrane activity. pH optima, cation requirements and heparin sensitivity of the detergent solubilized membrane activity were determined. Together these results suggest that protein kinases may be important modulators of protein assembly and function of the membrane skeleton of these protistan cells.     

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi

Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.      

Characterisation of a 34 kD protein from potato cyst nematodes, using monoclonal antibodies with potential for species diagnosis

Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations.