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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 59 (1997), S. 89-106 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The processes by which certain classes of toxic compounds or their metabolites may react with DNA to alter the genetic information contained in subsequent generations of cells or organisms are a major component of hazard associated with exposure to chemicals in the environment. Many classes of chemicals may form DNA adducts and there may or may not be a defined mechanism to remove a particular adduct from DNA independent of replication. Many compounds and metabolites that bind DNA also readily bind existing proteins; some classes of toxins and DNA adducts have the capacity to inactivate a repair enzyme and divert the repair process competitively. This paper formulates anintracellular dynamic model for one aspect of the action of toxins that form DNA adducts, recognizing a capacity for removal of those adducts by a repair enzyme combined with reaction of the toxin and/or the DNA adduct to inactivate the repair enzyme. This particular model illustrates the possible saturation of repair enzyme capacity by the toxin dosage and shows that bistable behavior can occur, with the potential to induce abrupt shifts away from steady-state equilibria. The model suggests that bistable behavior, dose and variation between individuals or tissues may combine under certain conditions to amplify the biological effect of dose observed as DNA aduction and its consequences as mutation. A model recognizing stochastic phenomena also indicates that variation in within-cell toxin concentration may promote jumps between stable equilibria.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biochemical genetics 33 (1995), S. 307-326 
    ISSN: 1573-4927
    Keywords: bilirubin-UDP-glucuronosyltransferase deficiency ; jaundice ; mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This report describes biochemical and cellular characterization of a spontaneous mutation in ICR mice; the mutation has been phenotypically characterized as autosomal recessive jaundice in neonates and juveniles and given the gene symbolhub (J. Hered. 76:441–446, 1985;Mouse Newslett. 73:28, 1985). The results obtained demonstrate that (1) mice homozygous for the mutation are deficient in bilirubin-UDP-glucuronosyltransferase activity, and there is no deficiency in heterozygous mice, (2) the deficiency is lifelong, even though the clinical symptom of jaundice is transitory and restricted to neonates or juveniles, (3) bilirubin-UDP-glucuronosyltransferase activity in mutant and nonmutant mice is similarly induced by triiodothyronine, (4) glucuronidation and xylodation of bilirubin probably occur as the result of separate enzyme forms in mice, and (5) Western analysis using antibody to rat bilirubin-UDP-glucuronosyltransferase indicates that although there is no electrophoretic mobility difference, there is a diffuse band missing in mutant mice. Hepatic hyperplasia, cytomegaly, single-cell necrosis, and eosinophilic foci are also pleiotropic traits associated with homozygous but not heterozygoushub. Thehub/hub mouse will be useful in the study of substrate specificity and regulation within a complex gene family and, perhaps, provide a new and useful animal model for the long-term health effects of deficiency in the metabolism of xenobiotics cleared via UDP-glucuronosyltransferase.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biochemical genetics 33 (1995), S. 307-326 
    ISSN: 1573-4927
    Keywords: bilirubin-UDP-glucuronosyltransferase deficiency ; jaundice ; mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This report describes biochemical and cellular characterization of a spontaneous mutation in ICR mice; the mutation has been phenotypically characterized as autosomal recessive jaundice in neonates and juveniles and given the gene symbolhub (J. Hered. 76:441–446, 1985;Mouse Newslett. 73:28, 1985). The results obtained demonstrate that (1) mice homozygous for the mutation are deficient in bilirubin-UDP-glucuronosyltransferase activity, and there is no deficiency in heterozygous mice, (2) the deficiency is lifelong, even though the clinical symptom of jaundice is transitory and restricted to neonates or juveniles, (3) bilirubin-UDP-glucuronosyltransferase activity in mutant and nonmutant mice is similarly induced by triiodothyronine, (4) glucuronidation and xylodation of bilirubin probably occur as the result of separate enzyme forms in mice, and (5) Western analysis using antibody to rat bilirubin-UDP-glucuronosyltransferase indicates that although there is no electrophoretic mobility difference, there is a diffuse band missing in mutant mice. Hepatic hyperplasia, cytomegaly, single-cell necrosis, and eosinophilic foci are also pleiotropic traits associated with homozygous but not heterozygoushub. Thehub/hub mouse will be useful in the study of substrate specificity and regulation within a complex gene family and, perhaps, provide a new and useful animal model for the long-term health effects of deficiency in the metabolism of xenobiotics cleared via UDP-glucuronosyltransferase.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 171-183 
    ISSN: 0148-7280
    Keywords: mouse ; spermatogenesis ; sperm differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A high frequency (42%) of sperm from the inbred homozygous mouse strain PL/J are abnormal. Head shape abnormalities occur in 15% of the total sperm; and 27% of the sperm are headless, with the mitochondria condensed into a mass at the caudal end of the midpiece region. The sperm without heads exhibit relatively normal motility. Electron microscopy of the testes indicates that some of the abnormal sperm in PL/J males result from a failure of the paired centrioles to attain a normal position on the nucleus opposite the acrosome prior to implantation, or to attach at all. The centrioles that are not attached to the nuclear envelope can differentiate to form the principal piece and midpiece region. The frequency of headless variants in heterozygous F1 indicates that the trait is mainly recessive. The offspring from the backcross of the F1 to homozygous PL/J parents did not give a clear-cut segregation pattern. The frequency of abnormal sperm in the F1 and the backcross is higher when the female parent is a PL/J.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 22 (1989), S. 399-410 
    ISSN: 0148-7280
    Keywords: gametogenesis ; mice ; Golgi apparatus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In an electron microscopy study of abnormal spermatogenesis in mice, we have found that two discrete haploid nuclei may be located in a single spermatid cytoplasm after the second meiotic division. The spermatid continues to differentiate and forms a binucleate spermatozoon with both nuclei separately packaged within the sperm head. The Golgi apparatus of the double spermatid forms a single proacrosome that attaches to both nuclei. Apparently, one acrosomal structure differentiates to cover and compartmentalize the two haploid nuclei within the sperm head. Chromatin condensation appears normal. The head morphology and number of flagella vary in mature spermatozoa produced by this process. This work demonstrates one pathway by which polyploid spermatids continue to differentiate to spermatozoa after failure of cytoplasmic division or possibly cellular fusion.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2018-09-13
    Description: High lethality rates associated with metastatic cancer highlight an urgent medical need for improved understanding of biologic mechanisms driving metastatic spread and identification of biomarkers predicting late-stage progression. Numerous neoplastic cell intrinsic and extrinsic mechanisms fuel tumor progression; however, mechanisms driving heterogeneity of neoplastic cells in solid tumors remain obscure. Increased mutational rates of neoplastic cells in stressed environments are implicated but cannot explain all aspects of tumor heterogeneity. We present evidence that fusion of neoplastic cells with leukocytes (for example, macrophages) contributes to tumor heterogeneity, resulting in cells exhibiting increased metastatic behavior. Fusion hybrids (cells harboring hematopoietic and epithelial properties) are readily detectible in cell culture and tumor-bearing mice. Further, hybrids enumerated in peripheral blood of human cancer patients correlate with disease stage and predict overall survival. This unique population of neoplastic cells provides a novel biomarker for tumor staging, as well as a potential therapeutic target for intervention.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 7
    Publication Date: 1995-10-01
    Print ISSN: 0006-2928
    Electronic ISSN: 1573-4927
    Topics: Biology , Chemistry and Pharmacology
    Published by Springer
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