No abstract

The increased use of UV radiation as a drinking water treatment technology has instigated studies of the repair potential of microorganisms following treatment. This study challenged the repair potential of an optimally grown nonpathogenic laboratory strain of Escherichia coli after UV radiation from low-and mediumpressure lamps. Samples were irradiated with doses of 5, 8, and 10 mJ/cm 2 from a low-pressure lamp and 3, 5, 8, and 10 mJ/cm 2 from a medium-pressure UV lamp housed in a bench-scale collimated beam apparatus. Following irradiation, samples were incubated at 37°C under photoreactivating light or in the dark. Sample aliquots were analyzed for up to 4 h following incubation using a standard plate count. Results of this study showed that E. coli underwent photorepair following exposure to the low-pressure UV source, but no repair was detectable following exposure to the medium-pressure UV source at the initial doses examined. Minimal repair was eventually observed upon medium-pressure UV lamp exposure when doses were lowered to 3 mJ/cm 2 . This study clearly indicates differences in repair potential under laboratory conditions between irradiation from low-pressure and medium-pressure UV sources of the type used in water treatment.

SUMMARYCells of an euploid strain of the Chinese hamster synchronized in the GI phase were microirradiated in the nucIeus with a laser UV microbeam (A=257 nm) and pulse-labelled with [3H]thymidine. In autoradiographs of cells fixed immediately after the pulse unscheduled DNA synthesis (UDS) was found restricted to tbe microirradiated part of the nueleus. Tbe rate of UDS varied with the UV energy applied and the post-irradiation incubation time. In other experiments chromosome preparations were established after an additional chase and a subsequent growth period. In 28 mitotic cells autoradiographic label was found concentrated on a few chromosomes which lay adjacent to each other in one part of the metaphase plate. The distribution of label on the chromosomes could clearly be distinguished from patterns wh ich originate from semi-conservative DNA synthesis within S phase. The label on chromosomes of microirradiated cells thus represents UDS. Dur findings support the following ideas on the arrangement of interphase chromosomes: (1) Decondensed interphase chromosomes may occupy rather compact territories. (2) Chromosomes do not necessarily exhibit a elose and permanent association with their respective homologues.Incorporation of [3H]thymidine into non-S phase cells (unscheduled DNA synthesis, UDS [1]) has been observed in cells of different origin after treatment with DNA damaging agents [2]. UDS observed after UV microirradiation of tissue culture cells [3][4][5][6][7][8][9] has recently been introduced as a tool to investigate the correlation of the chromosome arrangement in metaphase and in interphase. Sakharov et al. [8,9] performed UV microirradiation of anaphase chromosomes and used UDS to relocate the irradiated chromatin in the nuclei of daughter cells. An investigation of the arrangement of interphase chromosomes using this approach is, however, limited for two reasons: (a) In general chromosomes can be only very poody identified within a living mitotic cell; and (b) the arrangement established after irradiation might be abnormal due to UV-induced alterations (e.g. stickiness) of the irradiated chromatin [7]. These limitations do not apply to an approach in which the cell is irradiated du ring interphase and the irradiated chromatin is identified in chromosome preparations made in the following metaphase. In this case the cell is allowed to establish the interphase arrangement of chromosomes prior to irradiation. The identification of the irradiated chromatin in the next metaphase would allow to investigate this arrangement. This analysis Exp Cell Res /24 (/979)

Using cDNA probes for the human uvomorulin (UVO) and rat chymotrypsinogen B (CTRB) genes, we have analyzed two overlapping interstitial deletions on human chromosome 16q by Southern blot analysis. One deletion, with breakpoints at 16q22.1 and 16q22.3, results in loss of the UVO locus The second deletion, whose breakpoints are at 16q22.1 and 16q23.2, leads to loss of the CTRB locus. Therefore, UVO resides between both proximal deletion breakpoints within band 16q22.1 whereas CTRB is located between both distal breakpoints at 16q22.3 and 16q23.2.

Mutations in various ion channel genes are responsible for neuromuscular and other neurological disorders. We have previously identified the human small conductance calcium-activated potassium channel gene (hSKCa3) which has two tandemly arranged CAG repeats in its 5' region. Here we have isolated the first genomic clones containing the gene and have shown that both repeats are in exon 1. Homology to the previously localized sequence tagged site G16005 indicated that the gene may be on chromosome 22q, however using polymerase chain reaction amplification of somatic cell hybrid DNA and fluorescence in situ hybridization of two P1 artificial chromosome clones, we physically localized the gene to chromosome 1q21.3. We previously found an association between the highly polymorphic second (more 3') CAG repeat and schizophrenia in 98 patients and 117 controls. We have now genotyped an additional 19 patients with schizophrenia and have performed statistical analyses on the entire group of patients and controls to investigate the possible effect of age of onset, family history, and gender of the patients on the observed association. None of these factors were found to influence the results. Both CAG repeats have been typed in 86 bipolar I disorder patients, and no significant difference in allele distribution was observed between our bipolar disorder patients and controls.