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Biomedical subjects

L M Wagner

Publications and source records attributed to L M Wagner.

18 recordsLinked to original sources
PubMed2001

A virus-directed enzyme prodrug therapy approach to purging neuroblastoma cells from hematopoietic cells using adenovirus encoding rabbit carboxylesterase and CPT-11.

Tumor cells that contaminate hematopoietic cell preparations contribute to the relapse of neuroblastoma patients who receive autologous stem cell rescue as a component of therapy. Therefore, effective purging methods are needed. This study details in vitro experiments to develop a viral-directed enzyme prodrug purging method that specifically targets neuroblastoma cells. The approach uses an adenovirus to deliver the cDNA encoding a rabbit liver carboxylesterase that efficiently activates the prodrug irinotecan,7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11). The data show that an adenoviral multiplicity of infection of 50 transduces 100% of cultured neuroblastoma cells and primary tumor cells, irrespective of the level of tumor cell line contamination. Exposure of neuroblastoma cell lines or of mixtures of these cell lines with CD34(+) cells at a ratio of 10:90 to replication-deficient AdRSVrCE for 24 h and subsequent exposure of cells to 1-5 microM CPT-11 for 4 h increased the toxicity of CPT-11 to three neuroblastoma cell lines (SJNB-1, NB-1691, and SK-N-SH) from approximately 20-50-fold and eradicated their clonogenic potential. Also, after "purging," RNA for neuroblastoma cell markers (tyrosine hydroxylase, synaptophysin, and N-MYC) was undetectable by reverse transcription-PCR. In contrast, the purging protocol did not affect the number or type of colonies formed by CD34(+) cells in an in vitro progenitor cell assay. No bystander effect on CD34(+) cells was observed. The method described is being investigated for its potential clinical utility, particularly its efficacy for use with patients having relatively high tumor burdens, because no published methods have been shown to be efficacious when the tumor burden exceeds 1%.

Adenoviridae↗
PubMed2001

PKCalpha and PKCgamma overexpression causes lentoid body formation in the N/N 1003A rabbit lens epithelial cell line.

PURPOSE: The overexpression of PKCalpha or PKCgamma for extended periods of time causes the formation of lentoid bodies in the N/N 1003A rabbit lens epithelial cell line. To determine how differentiated the lentoid bodies are, we have looked for alphaA-, alphaB-, beta-, and gamma-crystallin levels in lentoid bodies after 4 and 8 weeks of lentoid body development. METHODS: Cells overexpressing PKCalpha or PKCgamma were plated in 6 well plates and were allowed to form lentoid bodies for up to 8 weeks. Lentoid bodies were fixed and stained with PKCalpha or PKCgamma antibodies along with either alphaA-, alphaB-, beta-, or gamma-crystallin antisera and viewed under a confocal microscope. Lentoid bodies were harvested in lysis buffer and homogenized. Fifty micrograms of protein per lane was loaded onto an SDS-PAGE gel and the bands transferred onto nitrocellulose. The blot was probed with either alphaA-, alphaB-, beta-, or gamma-crystallin antibodies for 12 h. Total RNA from lentoid bodies was isolated and 5 microg of total RNA was transcribed to first-strand cDNA. The PCR products were analyzed by 2% agarose gel electrophoresis. RESULTS: alphaB-crystallin was present in normal N/N 1003A cells and the lentoid bodies formed from PKCalpha and PKCgamma overexpression. alphaA-crystallin was only detectable in lentoid bodies after PKCalpha or PKCgamma overexpression. RT-PCR was able to detect beta-crystallin expression while the Western blot analysis and immunocytostaining detected small amounts of beta-crystallin protein. No gamma-crystallin expression was noted in these lentoid bodies. CONCLUSIONS: Overexpression of PKCalpha or PKCgamma in the N/N 1003A cell line induced lentoid body formation. These lentoid bodies expressed not only alphaB-crystallin but alphaA- and beta-crystallin. These results suggest a role for PKCs in lens epithelial cell differentiation to a fiber cell.

Animals↗
PubMed2001

Protein kinase C alpha and gamma in N/N 1003A rabbit lens epithelial cell differentiation.

PURPOSE: To determine if Protein Kinase C (PKC) plays a role in the initiation of lens epithelial cell differentiation into a lens fiber cell. METHODS: PKCalpha or PKCgamma was overexpressed in N/N 1003A lens epithelial cells for up to 7 days. Phase contrast microscopy was used to observe morphological changes associated with PKCalpha or PKCgamma overexpression. Cell cycle changes in cells overexpressing PKCalpha or PKCgamma were measured using acridine orange staining and flow cytometry. Crystallin levels in cells overexpressing PKCalpha or PKCgamma were measured using Western blots and RT-PCR. RESULTS: Significant differences in cell cycling were observed between untransfected cells and those overexpressing PKCalpha or PKCgamma. Overexpression of PKCalpha and PKCgamma caused the cells to lose their epithelial-like appearance and elongate. alphaB-crystallin expression was detected in all the samples while alphaA-crystallin was detected only in cells after 7 days of PKCalpha or PKCgamma overexpression. CONCLUSIONS: The observations that alphaA-crystallin is only found in N/N 1003A cells overexpressing PKCalpha or PKCgamma for 7 days along with the finding that a block in the G0/G1 phase of the cell cycle and the consequent morphological changes are observed, indicate that PKCalpha and PKCgamma may have a role in the initiation of differentiation in lens epithelial cells.

Acridine Orange↗
PubMed2001

Fractures in pediatric Ewing sarcoma.

PURPOSE: To determine the incidence, timing, and clinical significance of long-bone fractures in children with Ewing sarcoma family of tumors (ESFT). PATIENTS AND METHODS: We retrospectively reviewed 93 consecutive cases of ESFT of the long bones seen at a single institution over the course of a 37-year period. RESULTS: Fracture occurred in 14 (15%) of 93 patients with long-bone ESFT, most commonly in the femur. Approximately 30% of patients with tumors of the femur had fractures at some point in the course of their disease. The incidence of fracture was highest among patients with tumors of the proximal third of the femur (50%); these fractures were usually present at the time of initial diagnosis. Nine (64%) of the 14 fractures occurred after the start of radiotherapy, and three of these were associated with either local recurrence or second malignancy. CONCLUSIONS: Patients with femoral ESFT are at high-risk for fracture. If fractures occur after the completion of therapy, recurrence or second malignancy should be suspected.

Adolescent↗
PubMed2001

Haemopoietic growth factors in paediatric oncology: a review of the literature.

Recombinant haemopoietic growth factors (HGFs) are an attractive adjunct to reduce morbidity from chemotherapy regimens and their use has become widespread in paediatric oncology. Although patients receiving HGFs often have faster haematological recovery after intensive chemotherapy, this does not always translate into meaningful clinical benefits. This article reviews the clinical effectiveness of HGFs in a variety of different contexts. Most published studies have used granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) as prophylaxis to ameliorate the subsequent neutropenia following intensive chemotherapy. These 2 agents have also been used to mobilise peripheral blood stem cells for autologous transplantation. HGFs specific for anaemia and thrombocytopenia are currently in paediatric clinical trials and it is hoped that the proper context and administration strategy can be found to make their use clinically effective. This article also reviews data on toxicity, specifically focusing on differences between various formulations of growth factors. HGFs are expensive, and cost-benefit analyses reviewed in this article give an important perspective on the financial aspects of paediatric cancer care. Because HGFs do not benefit every child receiving chemotherapy and overuse increases costs and may result in unnecessary adverse effects, evidence-based guidelines for their rational use in paediatric oncology are proposed.

Anemia↗
PubMed2000

Escherichia coli thymidylate synthase expression protects human cells from the cytotoxic effects of 5-fluorodeoxyuridine more effectively than human thymidylate synthase overexpression.

In this study, we compared the relative abilities of human thymidylate synthase (hTS) and Escherichia coli thymidylate synthase (eTS) expression to confer resistance to the cytotoxic effects of treatment with the TS inhibitor 5-fluorodeoxyuridine (FdUrd). G418-selected clones expressing either form of the protein were significantly more resistant than the lacZ-expressing clone, VALZ2, to FdUrd-induced cytotoxicity. Although eTS-expressing clones expressed 2- to 3-fold more TS protein than hTS-overexpressing clones, the representative eTS-expressing clone, VAEG8, and hTS-overexpressing clone, VAHGC, were equally sensitive to an FdUrd-induced loss of clonogenicity; in addition, a large fraction of either form of exogenously expressed TS appeared to be inactive in the intact cell. The clones differed, however, in their responses to leucovorin (LV). Although LV significantly enhanced FdUrd-induced TS inhibition, growth inhibition, and cytotoxicity in VAHGC cells, it had no effect on these parameters in VAEG8 cells. These results suggest that eTS may more efficiently confer resistance to FdUrd plus LV when expressed for the purposes of a "host protection" strategy in vivo.

Cell Line↗
PubMed1998

Mechanism and pharmacological specificity of dUTPase-mediated protection from DNA damage and cytotoxicity in human tumor cells.

PURPOSE: We have reported previously that the expression of E. coli dUTPase (dutE) can protect HT29 cells from 5-fluorodeoxyuridine (FdUrd)-induced DNA fragmentation and cytotoxicity. In the study reported here, we further characterized the ability of dutE expression in one HT29 clone, dutE7, to alter the effects of treatment with FdUrd and other thymidylate synthase (TS) inhibitors. In addition, we developed two HuTu80 dutE-expressing clones using a pLNCX-dutE retroviral construct and tested their sensitivity to FdUrd-induced DNA fragmentation and cytotoxicity. METHODS: Both a dutE retroviral expression system and a dutE antibody were developed to facilitate the generation and screening of dutE-expressing clones. HT29 and HuTu80 clones expressing dutE were tested for drug-induced DNA damage with either alkaline elution or pulsed field gel electrophoresis and drug-induced loss of clonogenicity. RESULTS: Following a 24-h treatment with 100 microM CB3717 or 500 nM methotrexate (MTX), dutE7 cells were significantly less sensitive to drug-induced loss of clonogenicity than con3 cells. DutE7 cells were also resistant to CB3717-induced DNA fragmentation at 24 h. However, following a 48-h treatment with CB3717 or MTX there was no difference in survival between con3 and dutE7 cells, even though DNA damage was still greatly attenuated in the dutE7 cell line. In addition, expression of dutE in two HuTu80 clones, 80 C and 80 K, did not protect these cells from FdUrd-induced DNA damage or cytotoxicity. CONCLUSIONS: We conclude that the role of uracil misincorporation and subsequent DNA damage in cytotoxicity induced by TS inhibitors, in HT29 cells, is time dependent, and that cytotoxicity caused by long-term exposure to these drugs is largely independent of resultant DNA damage, in this cell line. The inability of dutE to protect HuTu80 cells from FdUrd further suggests that the significance of uracil misincorporation resulting from TS inhibition varies among cell lines.

Antineoplastic Agents↗
PubMed1995

Analysis of the short consensus repeats of human complement factor B by site-directed mutagenesis.

Human factor B is required for the initiation and propagation of the complement alternative pathway. It also participates in the amplification of the complement classical pathway. Alone, factor B is a zymogen with little known biochemical activity, but in the context of the alternative pathway convertases, the factor B serine protease is activated in a process that first involves the association with C3b and subsequently the cleavage of factor B into two fragments, Ba and Bb. Ba, the NH2-terminal fragment, is composed mainly of three tandem short consensus repeats, globular domains found in other complement proteins. It dissociates from the convertase during assembly, leaving the active C3 convertase, C3bBb. Previous reports suggest that the Ba region may be instrumental in convertase assembly. This hypothesis was tested using site-directed mutagenesis of recombinant factor B and monoclonal antibody epitope mapping to evaluate the relative importance of specific short consensus repeat amino acid residues. Three sites of interest were identified. Site 1 is a stretch of 19 contiguous amino acids in short consensus repeat 1 that form the epitope of a monoclonal antibody that effectively blocks factor B function. Site 2, composed of 6 contiguous amino acids in short consensus repeat 2, and site 3, consisting of 7 contiguous amino acids in short consensus repeat 3, were defined by mutations that reduce factor B hemolytic activity to 3% or less. Further analyses indicated that sites 2 and 3 contribute to factor B-C3b interactions.

Amino Acid Sequence↗
PubMed1995

Mouse complement regulatory protein Crry/p65 uses the specific mechanisms of both human decay-accelerating factor and membrane cofactor protein.

Normal host cells are protected from the destructive action of complement by cell surface complement regulatory proteins. In humans, decay-accelerating factor (DAF) and membrane cofactor protein (MCP) play such a biologic role by inhibiting C3 and C5 convertases. DAF and MCP accomplish this task by specific mechanisms designated decay-accelerating activity and factor I cofactor activity, respectively. In other species, including mice, structural and/or functional homologues of these proteins are not yet well characterized. Previous studies have shown that the mouse protein Crry/p65 has certain characteristics of self-protecting complement regulatory proteins. For example, Crry/p65 is expressed on a wide variety of murine cells, and when expressed on human K562 erythroleukemic cells, it prevents deposition of mouse C3 fragments on the cell surface during activation of either the classical or alternative complement pathway. We have now studied factor I cofactor and decay-accelerating activities of Crry/p65. Recombinant Crry/p65 demonstrates cofactor activity for factor I-mediated cleavage of both mouse C3b and C4b. Surprisingly, Crry/p65 also exhibits decay-accelerating activity for the classical pathway C3 convertase strongly and for the alternative pathway C3 convertase weakly. Therefore, mouse Crry/p65 uses the specific mechanisms of both human MCP and DAF. Although Crry/p65, like MCP and DAF, contains tandem short consensus repeats (SCR) characteristic of C3/C4 binding proteins, Crry/p65 is not considered to be a genetic homologue of either MCP or DAF. Thus, Crry/p65 is an example of evolutionary conservation of two specific activities in a single unique protein in one species that are dispersed to individual proteins in another. We propose that the repeating SCR motif in this family has allowed this unusual process of evolution to occur, perhaps driven by the use of MCP and DAF as receptors by human pathogens such as the measles virus.

Animals↗
PubMed1995

Cytotoxicity of ethylene oxide/propylene oxide copolymers in cultured mammalian cells.

Cytotoxicity was measured in vitro for 8 ethylene oxide/propylene oxide copolymers (EO/PO copolymers) using lactate dehydrogenase release from cultured mammalian cells as the endpoint. Three cell types were used in these assays: Chinese hamster ovary cell line (AS52), rat lung epithelial cell line (LEC), and freshly isolated rat alveolar macrophages (RAM). A range of cytotoxicity was seen with toxic effects observed from 20 to > 20,000 micrograms/ml. The same relative order of toxicities were observed for all 3 cell lines although RAM cells appeared to be somewhat more sensitive. The in vitro cytotoxicity, as measured by LDH release and microscopic observations of the cells, correlated poorly with the in vivo inhalation toxicity. The most lethal compounds following acute inhalation (UCON 50-HB-5100 and UCON 50-HB-2000) were among the least toxic in the in vitro cytotoxicity screen. Conversely the 2 compounds which were the most toxic in vitro (Pluronic 17 R1 and Pluronic L64) did not produce any unusual degree of toxicity in inhalation studies. The results of these experiments indicate that these in vitro mammalian cell assays will not be useful, at least for these classes of chemistry, in prediction of in vivo inhalation toxicity.

Animals↗
PubMed1994

Muscular fatigue and recovery following alternating isometric contractions at different levels of force.

The purpose of this study was to document the amount and rate of muscular fatigue during alternating levels of isometric contraction similar to that found during the Simulated Aerial Combat Maneuver (SACM). In addition, the time needed to recover from such an exercise was examined. Twenty males between the ages of 22 and 35 years performed an isometric contraction of their right quadriceps muscle at alternating levels of tension (20 and 50% maximum voluntary contraction) until exhaustion. The time at each contraction level was 10 s. After each exhaustive exercise bout, subjects were assigned to one of six recovery intervals (10, 20, 40, 60, 120, and 240 min) followed by a repeat of the exhaustive exercise. All subjects were tested under each of the six recovery intervals. Results showed that the amplitude (RMS) of the myoelectric signal increased while the frequency content of the signal (MPF) decreased over the course of the fatiguing activity. Endurance time (ET) was found to be significantly (p < 0.05) recovered (90.96%) within 60 min after stopping the exercise. Although MPF returned to its prefatigue value within 10 min of rest, the RMS value had still not recovered after 4 h.

Adult↗
PubMed1993

Psychology and survival.

We examined the deaths of 28,169 adult Chinese-Americans, and 412,632 randomly selected, matched controls coded "white" on the death certificate. Chinese-Americans, but not whites, die significantly earlier than normal (1.3-4.9 yr) if they have a combination of disease and birthyear which Chinese astrology and medicine consider ill-fated. The more strongly a group is attached to Chinese traditions, the more years of life are lost. Our results hold for nearly all major causes of death studied. The reduction in survival cannot be completely explained by a change in the behaviour of the Chinese patient, doctor, or death-registrar, but seems to result at least partly from psychosomatic processes.

Astrology↗
PubMed1992

Alterations in the structural gene and the expression of p53 in rat liver tumors induced by aflatoxin B1.

Rat hepatocellular carcinomas (HCCs) induced by aflatoxin B1 (AFB) treatment were examined for changes in the p53 tumor suppressor gene and in p53 suppressor gene expression. A high proportion of HCCs (nine of 11 tumors in six of eight animals) exhibited new p53 restriction fragments, indicating genomic alterations of one of the p53 alleles. Each tumor with an altered p53 restriction-fragment pattern exhibited a new fragment in one of two size classes (3 kb or 7 kb with EcoRI digestion) that were missing portions of the 3' end of the p53 gene. These findings indicate that apparently similar genomic rearrangements or deletions occurred independently in AFB-induced tumors. When compared with nontumor liver tissue from the same animal, the tumors with p53 gene alterations showed dramatically reduced levels of p53 mRNA and protein and greatly increased levels of histone H2B and retinoblastoma tumor suppressor (Rb) mRNA. In two HCCs showing no evidence of p53 restriction-fragment alterations, mutant p53 protein was detected. Mutant protein was also detected in two liver samples containing an adenoma and altered foci. These data suggest that alterations of the p53 tumor suppressor gene are involved in the induction of rat HCC by AFB.

Aflatoxin B1↗
PubMed1992

Analysis of the human regulators of complement activation (RCA) gene cluster with yeast artificial chromosomes (YACs).

The human regulators of complement activation gene cluster (RCA cluster) have been partially characterized with yeast artificial chromosomes (YACs). While the data confirm many points previously elucidated, the finer resolution of YAC mapping has allowed the discovery and/or localization of partial gene duplications, the determination of gene orientations, and the measurement of gaps between known genes. Here nine overlapping YACs that encompass a genomic region of 800 kb, encoding four RCA genes and three gene-like elements, are described. The encoded genes and two of the gene-like elements share the same orientation and are ordered (5' to 3') DAF, CR2, CR1, MCP-like, CR1-like, and MCP. A C4bp-like region lies upstream from DAF and is likely to correspond to one recently observed by F. Pardo-Manuel, J. Rey-Campos, A. Hillarp, B. Dahlback, and S. Rodriguez de Cordoba (1990, Proc. Natl. Acad. Sci. USA 87: 4529-4533). MCP-like, a new genetic element, was discovered and found to be homologous to the 5' portion of the MCP gene. Two large gaps of 85 kb (between CR2 and DAF) and 110 kb (between DAF and the C4bp-like element) could carry additional RCA genes. The arrangement of CR1, MCP-like, CR1-like, and MCP, in that order, strongly suggests that this region was generated by a single duplication of neighboring CR1/CR1-like and MCP/MCP-like forerunners. The RCA YACs will now serve as convenient DNA sources for the subcloning and further characterization of this region.

Amino Acid Sequence↗
PubMed1991

A bacterial system for investigating transport effects of cystic fibrosis--associated mutations.

LIV-I, a high-affinity system that transports neutral, branched-chain amino acids into Escherichia coli, has two components, LivG and LivF, that are homologous to the cystic fibrosis (CF) transmembrane conductance regulator (CFTR). CF-associated mutations of human CFTR were introduced into corresponding regions of LivG, and their effects on leucine transport could be grouped into three classes. Mutations were found that (i) abolished LIV-I--directed transport, (ii) retained about a quarter of wild-type activity at the Michaelis-Menten constant (KM), and (iii) had minimal activity at the KM. A mutation equivalent to a benign polymorphism had no effect on transport. The correlation of these mutational phenotypes in LivG and CFTR suggests that the LIV-I prokaryotic transporter is functionally similar to the CF protein and that this similarity can be exploited to clarify the properties of the nucleotide-binding fold in this superfamily of proteins.

ATP-Binding Cassette Transporters↗
PubMed1990

Nucleotide sequence and genetic characterization reveal six essential genes for the LIV-I and LS transport systems of Escherichia coli.

The nucleotide sequence of the genes encoding the high affinity, branched-chain amino acid transport systems LIV-I and LS has been determined. Seven genes are present on a 7568-base pair DNA fragment, six of which participate directly in branched-chain amino acid transport. Two periplasmic amino acid-binding proteins are encoded by the livJ (LIV-BP) and livK (LS-BP) genes. These two proteins confer specificity on the LIV-I and LS transport systems. livK is the first gene in a polycistronic message that includes four genes encoding membrane components, livHMGF. The protein products of the livHMGF genes are shared by the two systems. An analysis of the livH and livM DNA sequences suggests that they encode hydrophobic proteins capable of spanning the membrane several times. The LivG and LivF proteins are less hydrophobic, but are also tightly associated with the membrane. Both LivG and LivF contain the consensus sequence for adenine nucleotide binding observed in many other transport proteins. A deletion strain that does not express any of the liv genes was constructed. This strain was used to show that each of the membrane component genes is required for high affinity leucine transport, including two genes, livM and livF, for which no previous genetic evidence had been obtained.

Amino Acid Sequence↗
PubMed1986

Cloning, expression, and nucleotide sequence of livR, the repressor for high-affinity branched-chain amino acid transport in Escherichia coli.

The livR gene encoding the repressor for high-affinity branched-chain amino acid transport in Escherichia coli has been cloned from a library prepared from the episome F106. The inserted DNA fragment from the initial cloned plasmid, pANT1, complemented two independent, spontaneously derived, regulatory mutations. Subcloning as well as the creation of deletions with Bal31 exonuclease revealed that the entire regulatory region is contained within a 1.1-kb RsaI-SalI fragment. Expression of the pANT plasmids in E. coli minicells showed that the regulatory region encodes one detectable protein with an apparent molecular weight of 21,000. DNA sequencing revealed one open reading frame of 501 bp encoding a protein with a calculated MW of 19,155. The potential secondary structure of the regulatory protein has been predicted and it suggests that the carboxy terminus may fold into three consecutive alpha helices. These results suggest that the livR gene encodes a repressor which plays a role in the regulation of expression of the livJ and the livK transport genes.

Amino Acid Sequence↗