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Biomedical subjects

F F Becker

Publications and source records attributed to F F Becker.

At least 19 recordsLinked to original sources
PubMed1992

Alterations in expression and structure of the DNA repair gene XRCC1.

The repair-associated gene XRCC1 was previously cloned by complementing the hamster mutant EM9, which has a high rate of spontaneous SCE and hypersensitivity to DNA damaging agents. In analyzing XRCC1 gene expression, similar levels of steady-state mRNA were found in normal cells, Bloom's syndrome cells with altered SCE, and in squamous carcinoma cells with differential X-ray sensitivity. An EcoRI restriction fragment-length polymorphism previously identified in XRCC1 did not correlate with the repair phenotypes of these cells. The mRNA of XRCC1 decreased to 20-40% after treatment of cells with a DNA damaging agent. XRCC1 also showed tissue specific expression in rats. The mRNA levels were high in testis (7-8 fold), ovary (3-4 fold) and brain (4-5 fold), when compared with those in intestine, liver and spleen (1-2 fold). These data and the high levels of XRCC1 protein detected in testis indicate that XRCC1 may play an important role in DNA processing during meiogenesis and recombination in germ cells.

Amino Acid Sequence↗
PubMed1992

Identification of a specific inhibitor for DNA ligase I in human cells.

A protein inhibitor for human DNA ligase I has recently been identified. It was copurified with a fraction of the enzymes from HeLa cells through several steps of chromatography. The inhibitor was first identified by the absence of ligation activity of the associated enzyme, while it retained the ability to form the ligase-[32P]AMP adducts. The inhibitor was eluted as a single peak at approximately 0.25-0.30 M NaCl from a Mono S column. It inhibited the ligation of both double-stranded and single-stranded breaks by purified DNA ligase I but not by T4 DNA ligase and DNA ligase II. Subsequent gel-filtration chromatography indicated that this inhibitor, with a molecular mass of 55-75 kDa, could form a complex with DNA ligase I and inhibited the DNA ligation activity. Rechromatography of the ligase I-inhibitor complex in high-salt conditions resulted in the dissociation of the complex and the restoration of enzyme activity, indicating that the physical interaction of inhibitor with DNA ligase I is one of the mechanisms of inhibition. These data indicate that this protein inhibitor for DNA ligase I may play a specific role in regulating DNA ligation during replication, repair, or recombination.

Chromatography, Affinity↗
PubMed1992

Dual mode of inhibition of purified DNA ligase I from human cells by 9-beta-D-arabinofuranosyl-2-fluoroadenine triphosphate.

9-beta-D-Arabinofuranosyl-2-fluoroadenine (F-ara-A) is an analogue of adenosine and deoxyadenosine with potent anti-tumor activity. The mechanism of action for this compound has been elucidated as the inhibition of DNA and RNA synthesis, induction of DNA fragmentation, and genetic damage. This study demonstrated that DNA ligase I, an enzyme involved in DNA replication, is a target for the drug action. F-ara-adenine triphosphate (F-ara-ATP) at 80 microM inhibited the activity of DNA ligase I by more than 90%. In contrast, eight other related nucleoside analogues showed no effect on the enzyme activity at 200 microM. F-ara-ATP inhibited DNA ligation in two distinct ways. First, F-ara-ATP directly interacted with DNA ligase I and inhibited the formation of the ligase-AMP complex. This inhibition could not be reversed when free F-ara-ATP was eliminated from the treated enzyme; however, the addition of pyrophosphate, followed by gel filtration chromatography, restored enzyme activity, indicating that F-ara-ATP bound to the enzyme and altered the AMP-binding site. Secondly, the activity of DNA ligase I was inhibited when F-ara-ATP was incorporated into the 3' terminus of the DNA substrate. The dual mode of inhibition of DNA ligase I by F-ara-ATP indicates that its effect on DNA ligation may be important in the inhibition of DNA synthesis and the cytotoxicity of F-ara-A.

Adenosine Monophosphate↗
PubMed1992

New retractor for open rhinoplasty.

One of the problems often encountered in external rhinoplasty is retraction of the flap. When a wide, double-pronged retractor is used, the tongue of the external rhinoplasty flap falls between the two points, often obscuring the view of the tip-and-dome anatomy. When vein retractor-type instruments are used, they will often slip and do not stay stable. A retractor has been designed for external rhinoplasty that consists of a wide, double-pronged element to elevate the soft tissues of the lower third of the nose above the cartilaginous and bony anatomy, combined with a central, slightly set-back retractor that holds the tongue of the rhinoplasty flap in a secure, retracted position. This has been a significant improvement in retraction for the external rhinoplasty flap.

Humans↗
PubMed1991

Expression of specific UDP-glucuronosyltransferase isoforms in carcinogen-induced preneoplastic rat liver nodules.

The expression of specific UDP-glucuronosyltransferase isoforms in 2-acetylaminofluorane-induced rat liver preneoplastic nodules was studied; livers from pair-fed littermates were used as controls. For comparison, liver and kidney from 3-methylcholanthrene-treated or untreated (control) rats were used. Steady-state UDP-glucuronosyltransferase mRNA levels were determined by Northern blot analysis or in situ hybridization of tissue sections using a 30-mer oligonucleotide specific for the 3-methylcholanthrene-inducible UDP-glucuronosyltransferase (which is active toward 4-nitrophenol) or a double-stranded cDNA probe specific for androsterone-UDP-glucuronosyltransferase. For 3-methylcholanthrene-inducible UDP-glucuronosyltransferase, the mRNA level was very low in control liver; there was a 15-fold increase after 3-methylcholanthrene treatment. This mRNA was present at relatively high concentration in the kidney and there was a threefold increase after 3-methylcholanthrene administration. In livers with preneoplastic nodules 1 mo after cessation of carcinogen administration, this mRNA concentration was approximately 15 times greater than in control liver. Similar changes in the level of the 3-methylcholanthrene-inducible UDP-glucuronosyltransferase were also observed by in situ hybridization of tissue sections. Immunocytochemical studies using an antiserum that recognizes the 3-methylcholanthrene-inducible UDP-glucuronosyltransferase showed a marked increase in the concentration of this isoform in preneoplastic nodules compared with the adjacent nonnodular liver.

2-Acetylaminofluorene↗
PubMed1991

Specific reduction of I-compound levels in DNA from spontaneous hepatomas of 22-24 month old male C3H mice.

As previously shown by 32P-postlabeling, I-compound levels are reduced in target tissue DNA of animals exposed to one of several non-genotoxic hepatocarcinogens, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin, carbon tetrachloride, peroxisome proliferators and choline-devoid diet. I-compound levels are further reduced, sometimes to undetectable levels, in chemically induced, transplantable rat (Morris) hepatomas and hepatocellular carcinomas induced by peroxisome proliferators or choline-devoid diet. The current study investigated I-compounds in spontaneous hepatic adenomas of genetically susceptible male C3H mice. DNA samples from individual tumors, background livers (non-tumor bearing lobe from tumor bearing mouse) and non-tumor bearing normal livers taken from 22-24 month old animals were analyzed by 32P-postlabeling. I-compound profiles were qualitatively comparable among the three types of tissues. However, levels of most I-compounds were 2.6-5.0 times lower in tumors than in background liver and non-tumor bearing normal liver. There were virtually no differences between background liver and normal liver. Taken together with the previously reported I-compound deficiency in carcinogen-induced hepatomas, the present observations on genetically initiated neoplasms suggest that this phenomenon may play a role in hepatocarcinogenesis and maintenance of neoplasia.

Aging↗
PubMed1991

Suppression of in vitro chemical transformation by the carcinogenesis-promoting, viable yellow gene Avy.

The presence of the viable yellow Avy and lethal yellow Ay genes has been demonstrated to accelerate the process of tumorigenesis in mice bearing genetically, chemically or virally initiated cells. This promoting effect has been reported in the liver, lung, breast, bladder and skin. Although it has been demonstrated that the accelerated process is associated with systemic, pathophysiologic alterations such as an alteration in the lipogenic pathway, which in turn leads to obesity, alteration in glucose metabolism and/or random immunologic alterations, no examination of the in vitro 'tumorigenic' susceptibility of the cells of animals bearing the yellow genes has yet been reported. In the current study, spontaneous and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced transformation was determined in skin-derived fibroblasts from C57BL/6N-Avy/a mice (Hy) and their black a/a litter mates (B1-). The growth rate of untreated fibroblasts was greater for those from the yellow mice than from the black, while susceptibility to MNNG toxicity was equivalent. However, the rate of spontaneous and chemically induced transformation was consistently and significantly higher in the cells obtained from the black a/a mice than in those from yellow, Avy/a litter mates. These findings, with others from the literature, suggest that the Avy gene may suppress transformation and carcinogenic susceptibility in specific cells, such as fibroblasts, while the systemic effects of the gene are promotional in other cells.

Animals↗
PubMed1991

IL-2-dependent murine T-cell lines and clones expressing gamma/delta T-cell antigen receptors. I. Functional and biochemical characterization.

We have developed two stable IL-2-dependent T-cell lines designated AKV-I and AKV-N from the enlarged spleens, respectively, of an AKV1 and an NFS mouse. Immunofluorescence staining with the appropriate monoclonal antibodies revealed that cells of the AKV-I cell line were alpha beta TCR-CD3+CD4-CD5-CD8+CD25+, whereas cells of the AKV-N cell line were alpha beta TCR-CD3+CD4-CD5+CD8-CD25+. A number of T-cell clones were developed from the AKV-I or AKV-N T-cell lines by limiting dilution and analysed by immunofluorescence. All clones tested were alpha beta TCR-CD3+CD4-CD25+. Certain T-cell clones expressed the CD5 antigen, whereas others expressed the CD8 antigen. The AKV-I cell line responded by proliferation to rIL2, rIL4, phorbol myristate acetate (PMA), PMA plus IL-4 and PMA plus PHA or Con A. In contrast, the AKV-N cell line did not respond to rIL-4 or rIL-4 plus PMA and exhibited only a modest proliferative response to PMA alone. Both AKV-I and AKV-N T-cell lines as well as a large number of T-cell clones examined were able to lyse cells of the PU5-IR murine cell line in the presence of the anti-CD3 (clone 145-2C11) MoAb, demonstrating their ability to mediate cytotoxicity in this system. Biochemical analysis of both AKV lines and a number of clones by immunoprecipitation with the anti-CD3 MoAb, followed by one-dimensional (either non-reducing or reducing) or two-dimensional (non-reducing/reducing) SDS-PAGE, revealed that the AKV lines and clones expressed a disulphide-linked dimer. Under non-reducing conditions, a band in the range of 75-85 kDa was observed and upon reduction it was resolved into two discrete polypeptide chains of 43-44 kDa and 48 kDa in certain AKV-I cells or 38 kDa and 42 kDa in certain AKV-N cells. In other T-cell clones or lines a broad band of 42-47 kDa was observed in AKV-I cells or 38-45 kDa in AKV-N cells. These results suggest the presence of different forms of disulphide-linked dimers on these cells. Northern blotting analysis using probes specific for the constant regions of the alpha-, beta-, gamma- and delta-chains of the T-cell antigen receptor revealed that all the AKV cell lines or clones tested expressed full-length alpha-, gamma- and delta-chain mRNA, whereas beta-chain mRNA was absent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Fingerprinting of near-homogeneous DNA ligase I and II from human cells. Similarity of their AMP-binding domains.

DNA ligases play obligatory roles during replication, repair, and recombination. Multiple forms of DNA ligase have been reported in mammalian cells including DNA ligase I, the high molecular mass species which functions during replication, and DNA ligase II, the low molecular mass species which is associated with repair. In addition, alterations in DNA ligase activities have been reported in acute lymphocytic leukemia cells, Bloom's syndrome cells, and cells undergoing differentiation and development. To better distinguish the biochemical and molecular properties of the various DNA ligases from human cells, we have developed a method of purifying multiple species of DNA ligase from HeLa cells by chromatography through DEAE-Bio-Gel, CM-Bio-Gel, hydroxylapatite, Sephacryl S-300, Mono P, and DNA-cellulose. DNA-cellulose chromatography of the partially purified enzymes resolved multiple species of DNA ligase after labeling the enzyme with [alpha-32P]ATP to form the ligase-[32P]AMP adduct. The early eluting enzyme activity (0.25 M NaCl) contained a major 67-kDa-labeled protein, while the late eluting activity (0.48 M NaCl) contained two major labeled proteins of 90 and 78 kDa. Neutralization experiments with antiligase I antibodies indicated that the early and late eluting activity peaks were DNA ligase II and I, respectively. The three major ligase-[32P]AMP polypeptides (90, 78, and 67 kDa) were subsequently purified to near homogeneity by elution from preparative sodium dodecyl sulfate-polyacrylamide gels. All three polypeptides retained DNA ligase activities after gel elution and renaturation. To further reveal the relationship between these enzymes, partial digestion by V8-protease was performed. All three purified polypeptides gave rise to a common 22-kDa-labeled fragment for their AMP-binding domains, indicating that the catalytic sites of ligase I and II are quite similar, if not identical. Similar findings were obtained from the two-dimensional gel electrophoresis of their AMP-binding domains in the trypsin-digested protein fragments. The results also suggested that these isozymes have been derived from the same primordial DNA sequence or from the same precursor protein. The purification scheme and the data obtained will be instrumental for the further elucidation of the biological roles of various DNA ligases from human cells.

Adenosine Monophosphate↗
PubMed1990

Role of the AKR gene locus AKv-1 in susceptibility to chemical induction of thymic lymphomas.

Various strains of mice demonstrate widely differing susceptibility to chemical induction of thymic lymphomas, in both timing and incidence. In AKR mice tumors appear very early and at high incidence after a single dose of N-methyl-N-nitrosourea, while in other strains they appear later and at lower incidences. In an attempt to determine the potential role of AKR ecotropic murine leukemia virus loci in this process, congenic mice of NFS/N background, into which the highly productive ecotropic murine leukemia virus loci AKv-1 or AKv-2 has been transferred, were challenged with N-methyl-N-nitrosourea. Although they had a lower incidence of thymic lymphomas than did the parental donor AKR, the NS.AKv-1 mice had a tumor incidence twice that of NFS/N or NS.AKv-2. However, no difference in timing was noted, and these three strains demonstrated tumor appearance much later than that of AKR/N. It is suggested that the presence of the AKv-1 loci, or a gene of the closely associated genomic region, increases the number of target cells that are susceptible to N-methyl-N-nitrosourea.

Alleles↗
PubMed1990

Dielectrophoretic characterisation of Friend murine erythroleukaemic cells as a measure of induced differentiation.

Dielectrophoresis measurements, the study of the motion of particles in non-uniform a.c. electrical fields, have been made on three cell lines (DS19, R1 and DR1) of Friend murine erythroleukaemia cells as a function of hexamethylene bisacetamide (HMBA) treatment. The effects of saponin treatment on R1 cells and neuraminidase on human red blood cells were also studied. It is shown that the dielectrophoretic behaviour can be interpreted in terms of cell surface charge and cell membrane conductivity effects. HMBA reduces the cell surface charge on all three cell lines, and in lines DS19 and DR10, where the cells are induced to differentiate, there is an increase in effective cell conductivity. This gain in conductivity is concluded to be associated with either an enhanced lateral electrophoretic motion of delocalised ions or of the polarisability of dipoles at the membrane surface.

Acetamides↗
PubMed1990

Heme synthesis in normal mouse liver and mouse liver tumors.

Hepatic cancers from mice and rats demonstrate decreased levels of delta-aminolevulinic acid synthase, the rate-limiting enzyme in the heme synthetic pathway, and increased heme oxygenase, the heme-catabolizing enzyme. These findings suggest that diminution of P-450, b5, and catalase in these lesions may result from a heme supply that is limited by decreased heme synthesis and increased heme catabolism. Heme synthesis was measured in mouse liver tumors (MLT) and adjacent tumor-free lobes (BKG) by administering the radiolabeled heme precursors 55FeCl3 and [2-14C]glycine and subsequently extracting the heme for determination of specific activity. Despite reduced delta-aminolevulinic acid synthase activity in MLT, both tissues incorporated [2-14C]glycine into heme at similar rates. At early time points, heme extracted from MLT contained less 55Fe than that from BKG. This was attributed to the findings that MLT took up 55Fe at a slower rate than BKG and had larger iron stores than BKG. The amount of heme per milligram of protein was also similar in both tissues. These findings militate against the hypothesis that diminished hemoprotein levels in MLT result from limited availability of heme. It is probable, therefore, that decreased hemoprotein levels in hepatic tumors are linked to a general program of dedifferentiation associated with the cancer phenotype. Diminution of hemoprotein in MLT may result in a relatively increased intracellular heme pool. delta-Aminolevulinic acid synthase and heme oxygenase are, respectively, negatively and positively regulated by heme. Thus, their alteration in MLT may be due to the regulatory influences of the heme pool.

Animals↗
PubMed1990

Submental W-plasty for correction of 'turkey gobbler' deformities.

There are many causes and types of submental contour deformities. One such deformity called a turkey gobbler, is caused by an excess of flaccid submental skin and as an isolated defect is seen more commonly in men. We have found that skin excision and a running submental W-plasty for correction of this deformity yields a superior cosmetic result with excellent camouflage of the submental scar. Two cases are illustrated.

Chin↗
PubMed1990

Alterations in electrophoretic mobility, diaphorase activity, and terminal differentiation induced in murine erythroleukemia lines by differentiating agents.

The electrophoretic mobilities (EPMs) and semiquinone reductase activities of two clones of Friend murine erythroleukemia (MEL) cells were investigated as a function of treatment with the inducing agents dimethylsulfoxide (DMSO) and hexamethylene bisacetamide (HMBA). As reported previously by others, the inducible clone DS19 lost its ability to grow in soft agar and expressed hemoglobin as judged by benzidine/H2O2 staining after 96 hours of treatment with 1% DMSO or 4 mM HMBA. In addition, its EPM fell by 14%, its semiquinone reductase activity by 40%, and its mean diameter by 10%. The second clone, R1, retained its ability to grow in soft agar and lacked hemoglobin expression after treatment with HMBA and DMSO, characterizing it as noninducible. However, R1 did demonstrate alterations in EPM, semiquinone reductase activity, and cell diameter that closely paralleled those found in DS19. Such responses were not seen in three non-MEL cell lines exposed to HMBA or DMSO, suggesting that clone R1 responded to these inducing agents in a cell-line specific manner but that its ability to complete the sequences necessary for differentiation may be blocked at an unknown point distal to the block characteristic of untreated cells. The data show that while a reduction in EPM, semiquinone reductase activity, and cell diameter accompany induced differentiation in MEL cells, such changes can occur in the absence of a commitment to terminal differentiation.

Acetamides↗
PubMed1990

Overexpression of the multidrug resistance gene mdr3 in spontaneous and chemically induced mouse hepatocellular carcinomas.

Overexpression of a family of plasma membrane glycoproteins, known as P-glycoproteins, is commonly associated with multidrug resistance in animal cells. In rodents, three multidrug resistance (mdr or pgp) genes have been identified, but only two can confer the multidrug resistance phenotype upon transfection into animal cells. Using the RNase protection method, we demonstrated that the levels of three mdr gene transcripts differ among mouse tissues, confirming a previous report that the expression of these genes is tissue specific (J.M. Croop, M. Raymond, D. Huber, A. DeVault, R. J. Arceci, P. Gros, and D. E. Housman, Mol. Cell. Biol. 9:1346-1350, 1989). The levels of mdr transcripts were determined for mouse liver tumors spontaneously arising in both C3H/HeN and transgenic animals containing the hepatitis B virus envelope gene and for tumors induced by two different carcinogenic regimens in C57BL/6N and B6C3-F1 mice. The mdr3 gene was overexpressed in all 22 tumors tested. Our results demonstrate that overexpression of the mdr3 gene in mouse liver tumors does not require exposure of the animals to carcinogenic agents and suggest that its overexpression is associated with a general pathway of hepatic tumor development. The overexpression of the mdr3 gene, which is the homolog of human mdr1 gene, in hepatocellular carcinomas may be responsible for the poor response of these tumors to cancer chemotherapeutic agents.

1,2-Dimethylhydrazine↗
PubMed1990

External approach to rhinoplasty.

The external approach to rhinoplasty offers several distinct advantages over the classical endonasal approach for incising, excising, repositioning, and augmenting the framework of the nose for functional and aesthetic improvement. The history of external rhinoplasty, advantages and alleged disadvantages are discussed; personal experience since 1982 is outlined. Various nasal deformities which have been corrected using the external approach are listed and several are discussed and illustrated. This report presents an overview of the technique of external rhinoplasty which will become even more popular as the advantages continue to be recognized by more nasal surgeons.

Female↗