Preferential expression of cellular retinoic acid binding protein in a subpopulation of neural cells in the developing mouse embryo

The cellular retinoic acid binding protein is thought to be involved in the retinoic-acid-mediated signal transduction pathway. We have isolated the mouse cellular retinoic acid binding protein cDNA from an embryonal-carcinoma-derived cell line by using differential cDNA cloning strategies. In situ hybridization on sections of mouse embryos of various developmental stages indicated that the cellular retinoic acid binding protein gene, which we localized on mouse chromosome 9, is preferentially expressed in a subpopulation of neurectodermal cells. This restricted expression pattern suggests an important role for cellular retinoic acid binding protein in murine neurogenesis.     

Localization of a gene involved in complementation of the defect in xeroderma pigmentosum group A cells on human chromosome 1

Human, Chinese hamster or Chinese hamster/human hybrid cytoplasts were fused with UV-irradiated xeroderma pigmentosum group A (XP-A) cells. Unscheduled DNA synthesis (UDS) of the XP-A nucleus was measured 0-2 and 2-4 h after seeding of the fused population. Human cytoplasts did correct the defect in the XP-A nucleus immediately after fusion, whereas the chinese hamster cytoplasts did not show this rapid increase in excision repair. The results obtained after fusion of cytoplasts isolated from a panel of 26 Chinese hamster-human hybrids showed that chromosome 1 bears genetic information that is necessary for the rapid correction of the XP-A defect. Furthermore, this genetic information was regionally assigned to 1q42-qter by analysing hybrid cell lines having retained various segments of chromosome 1. Cytoplasts from a Chinese hamster/XP-A hybrid containing chromosome 1 of XP-A origin corrected also the defect with fast kinetics. This result indicate that the correcting factor consists of human and Chinese hamster components. As a consequence, the gene mapped on chromosome 1 may not be the gene which is mutated in XP-A cells.     

Genetic complementation analysis of ataxia telangiectasia and Nijmegen breakage syndrome: a survey of 50 patients

Cultured cells from patients with ataxia telangiectasia (AT) or Nijmegen breakage syndrome (NBS) are hypersensitive to ionizing radiation. After radiation exposure, the rate of DNA replication is inhibited to a lesser extent than in normal cells, whereas the frequency of chromosomal aberrations is enhanced. Both of these features have been used in genetic complementation studies on a limited series of patients. Here we report the results of extended complementation studies on fibroblast strains from 50 patients from widely different origins, using the radioresistant DNA replication characteristic as a marker. Six different genetic complementation groups were identified. Four of these, called AB, C, D, and E (of which AB is the largest), represent patients with clinical signs of AT. Patients having NBS fall into two groups, V1 and V2. An individual with clinical symptoms of both AT and NBS was found in group V2, indicating that the two disorders are closely related. In AT, any group-specific patterns with respect to clinical characteristics or ethnic origin were not apparent. In addition to the radiosensitive ATs, a separate category of patients exists, characterized by a relatively mild clinical course and weak radiosensitivity. It is concluded that a defect in one of at least six different genes may underlie inherited radiosensitivity in humans. To facilitate research on defined defects, a complete list of genetically characterized fibroblast strains is presented.     

Anaerobic degradation of papermill sludge in a two-phase digester containing rumen microorganisms and colonized polyurethane foam

Summary The use of reticulated polyurethane foam as a support material for the immobilization of methanogenic associations and its application to the anaerobic treatment of fine particulate solid wastes was investigated. The colonization of polyurethane support particles in a continuous upflow reactor fed on a mixture of acetate, propionate and butyrate, was both rapid and dense. The combination of rumen microorganisms and colonized support particles in a two-phase digester resulted in an efficient anaerobic decomposition of papermill sludge.     

Transfection of the cloned human excision repair gene ERCC-1 to UV-sensitive CHO mutants only corrects the repair defect in complementation group-2 mutants

The human DNA-excision repair gene ERCC-1 is cloned by its ability to correct the excision-repair defect of the ultraviolet light- and mitomycin-C-sensitive CHO mutant cell line 43-3B. This mutant is assigned to complementation group 2 of the excision-repair-deficient CHO mutants. In order to establish whether the correction by ERCC-1 is confined to CHO mutants of one complementation group, the cloned repair gene, present on cosmid 43-34, was transfected to representative cell lines of the 6 complementation groups that have been identified to date. Following transfection, mycophenolic acid was used to select for transferants expressing the dominant marker gene Ecogpt, also present on cosmid 43-34. Cotransfer of the ERCC-1 gene was shown by Southern blot analysis of DNA from pooled (500-2000 independent colonies) transformants of each mutant. UV survival and UV-induced UDS showed that only mutants belonging to complementation group 2 and no mutants of other groups were corrected by the ERCC-1 gene. This demonstrates that ERCC-1 does not provide an aspecific bypass of excision-repair defects in CHO mutants and supports the assumption that the complementation analysis is based on mutations in different repair genes.     

Localization of two human homologs, HHR6A and HHR6B, of the yeast DNA repair gene RAD6 to chromosomes Xq24-q25 and 5q23-q31.

The chromosomal localizations of two closely related human DNA repair genes, HHR6A and HHR6B, were determined by in situ hybridization with biotinylated probes. HHR6A and HHR6B (human homolog of yeast RAD6) encode ubiquitin-conjugating enzymes (E2 enzymes), likely to be involved in postreplication repair and induced mutagenesis. The HHR6B gene was assigned to human chromosome 5q23-q31, whereas the HHR6A gene was localized on the human X chromosome (Xq24-q25). This latter assignment was confirmed with an X-specific human-mouse/hamster somatic cell hybrid panel. Southern blot analysis points to an X and an autosomal localization of HHR6A and HHR6B, respectively, in the mouse. The potential involvement of these genes in human genetic disorders is discussed.     

Hydrocephalus and red-disease in pike fry Esox lucius L.

Two diseases of pike fry have been investigated, both causing serious losses in Dutch pike culture. In one of these diseases the lump developing on the head of the fry was associated with an internal hydrocephalus.
The other one, 'red disease' after the haemorrhagic areas in the trunk, may be identical with red-sore disease of pike.
The etiologies of both diseases are unknown.     

The induction of chromosomal damage and cell killing in mouse spermatogonial stem cells following combined treatments with hydroxyurea, 3-aminobenzamide and X-rays

To analyze in more detail the relation between the sensitivity of spermatogonial stem cells to killing and the induction of genetic damage, mature male mice received combined treatments with hydroxyurea (HU), 3-aminobenzamide (3-AB) and X-rays. Stem cell killing was determined using the repopulation index method and translocations were studied via spermatocyte analysis. HU was administered at 16 or at 48 h before further treatment in order to create stem cell populations with different sensitivities in whic the translocation induction and stem cell killing could be studied and compared. The sensitivities for cell death and genetic damage appeared to be strongly correlated: at 16 h after HU significantly higher values were found than at 48 h or in controls without HU pretreatment.By using 3-AB in the treatment schedules we were able to investigate whether the sensitization of stem cells towards cell death and genetic damage is the outcome of a radiation- or drug-induced G₁ delay. The effect of 3-AB was most pronounced at 16 h after HU. This confirms that at this interval a large fraction of stem cells is in G₁. Our data therefore indicate that all treatments that induce an enrichment of G₁ cells also result in a sensitization of stem cells to cell killing or the induction of mutagenic damage.