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D L Bronson

Publications and source records attributed to D L Bronson.

At least 19 recordsLinked to original sources
PubMed1996

Synthesis and analysis of a 640-bp pol region of novel human endogenous retroviral sequences and their evolutionary relationships.

Nucleotide sequence comparisons of the pol gene among 47 retroelements identified two very conserved regions, separated by a span of approximately 640 bp, that have not been previously reported. A set of mixed oligonucleotide primers, 5'-MOP-2 and 3'-MOP-2, homologous to these two conserved pol regions was constructed for use in detection of retroelements. When MOPs-2 were employed in PCR amplification studies, products of about 0.64 kb in size were amplified from human and mouse genomic DNAs and from HIV-1 proviral DNA, but not from negative control plasmid DNAs. The PCR products amplified with MOPs-2 from human LuC-1 teratocarcinoma cell DNA were subcloned and sequenced. Five clones of approximately 0.64 kb in size were identified, and sequence comparisons with all entries in GenBank indicated that these five clones have highest homology, in a range of 64.31 to 98.65%, with the corresponding pol region of HERV-K10 and HM-16 of the human endogenous retrovirus-K (HERV-K) family. Southern hybridizations at high stringency demonstrated that these five clones are present in all human DNAs tested. The evolutionary relationships of these clones with the equivalent pol region of other retroelements were defined by phylogenetic analyses that placed three clones into the HERV-K family and two clones into a new family of human endogenous retroelements. In addition, clone HERV-(K)73 contains the smaller PV1b pol segment that was reported to be selectively expressed in blood leukocytes of patients with polycythemia vera.

Amino Acid Sequence↗
PubMed1995

Restricted expression of new HERV-K members in human teratocarcinoma cells.

Northern hybridization with five HERV-K family members, previously cloned from human teratocarcinoma genomic DNA, indicated that two (HERV-(K)27 and -(K)67) of the five clones are expressed in these teratocarcinoma cells. These two clones are closely related (98.49%), however, and Northern blot hybridization lacks the specificity to distinguish between their respective mRNAs. Therefore, PCR analysis with mixed oligonucleotide primers homologous to conserved retroviral pol gene regions was employed to amplify cDNA synthesized from teratocarcinoma cell RNA. This amplification scheme yielded two novel HERV-K family members, HERV-(K)55 and HERV-(K)91. Clone HERV-(K)55 has approximately 98% nucleotide sequence identity to clones HERV-(K)27 and -(K)67. Subsequent RNase protection assays confirmed the expression of HERV-(K)55 and indicated that clones HERV-(K)27 and -(K)67 were not expressed in these cells. One interpretation is that the HERV-(K)27 and -(K)67 probes detected transcripts of clone HERV-(K)55 or other closely-related elements because of their high homologies. In addition, clone HERV-(K)91, which has approximately 81% nucleotide sequence identity to clones HERV-(K)27, -(K)67, and -(K)55, was obtained only from teratocarcinoma 2102E-Pr cells, but the RNase protection assay showed that this clone is also expressed in other human teratocarcinoma cell lines.

Base Sequence↗
PubMed1995

Phylogenetic analyses of 55 retroelements on the basis of the nucleotide and product amino acid sequences of the pol gene.

Comparisons of pol gene nucleotide and reverse transcriptase (RT) amino acid sequences of 47 retroviruses, 3 caulimoviruses, and 5 hepadnaviruses showed that approximately one-third of the gene at the 5' end is much more conserved than other pol regions. The most conserved regions on both the nucleotide and amino acid sequences were chosen for construction of phylogenetic trees. The maximum-parsimony and distance-matrix methods were used for analyses of aligned amino acid sequences; these two methods, and the compatibility method, were used to analyze the aligned nucleotide sequences. Essentially identical majority-rule consensus trees were produced by these different methods from both the pol gene nucleotide and RT amino acid sequences, which divided the 55 retroelements into six major groups. The reliability of the phylogenetic trees was probed with the bootstrapping of 100 replicates of the original sequence alignments. The grouping results were shown to be statistically significant by multiple comparisons with the least-significant-difference procedure.

Amino Acid Sequence↗
PubMed1994

Replication error-type genetic instability at 1q42-43 in human male germ cell tumors.

The replication error phenotype, recognized as microsatellite sequence alterations, has recently been suggested to be associated with hereditary nonpolyposis colorectal cancer and other types of sporadic tumors. We examined paired tumor-normal DNAs from 69 human male germ cell tumors for somatic instability at the 1q42-43 region. Analysis of a variable number of tandem repeats marker (D1S74) and 3 (CA)n type microsatellite loci (D1S235, D1S180, and angiotensinogen) revealed genetic alterations in tumor DNAs of 26 (38.2%) cases. The changes observed comprised rearrangements with D1S74 detected by Southern blot analysis in 4 of 55 (7%) cases; replication error-type alterations with D1S235, D1S180, and angiotensinogen in 12 of 66 (18.2%) cases; and loss of heterozygosity in 12 of 67 (17.9%) cases with the same probes. The microsatellite sequence alterations were more common in histological subsets other than teratomas, while the loss of heterozygosity was significantly more frequent in teratomas compared to other histologies. These results suggest that microsatellite instability and loss of heterozygosity at 1q42-43 may be unrelated genetic events which may play a role in germ cell tumor development.

Chromosomes, Human, Pair 1↗
PubMed1994

Frequent allelic deletions and loss of expression characterize the DCC gene in male germ cell tumors.

The DCC tumor suppressor gene has been shown to be frequently deleted or its expression reduced or absent in colorectal, gastro-intestinal, pancreatic, prostatic, and breast carcinomas, and glioblastomas. By allelotype analysis using the DCC-flanking polymorphic marker D18S5 we have previously shown that allelic deletions at 18q21 occur in 40% of male germ cell tumors (Murty et al., 1994). In order to further understand the role of DCC gene in germ cell tumorigenesis, we evaluated deletions by loss of heterozygosity (LOH) and mRNA expression by RT-PCR in tumor tissues and cell lines. Analysis of 61 paired normal-tumor DNAs using the probes D18S5, JOSH 4.4 (a polymorphism within the DCC locus) and a (CA)n polymorphism in an intron of DCC revealed that 45% of GCTs had allelic deletions. In addition, two homozygous deletions were found in the DCC gene among 91 (61 used in the LOH analysis and an additional 30) tumor DNAs when screened with the cDNA probes (pDCC 1.65, pDCC 1.9 and pDCC 1.0). By RT-PCR analysis of four normal testes, nine GCT cell lines and 14 tumor tissues, DCC gene expression was detected in all four normal testes, while four (45%) GCT cell lines and one (7%) tumor specimen showed lack of expression. In addition, DCC expression was highly reduced in three (21%) tumor tissues. The high frequency of LOH at 18q21 was characteristic of seminomas as well as all subsets of non-seminomas in primary as well as metastatic states. Frequent allelic loss in all histologic subsets, homozygous deletions, and loss of expression of DCC suggest that suppression of this gene's function is an early event in GCT development.

Alleles↗
PubMed1991

Plasma protein and apolipoprotein synthesis by human yolk sac carcinoma cells in vitro.

Three human yolk sac carcinoma cell lines were characterized for the expression of several markers. Each of the cell lines expressed alpha-fetoprotein, without detectable levels of chorionic gonadotropin, and the level of alpha-fetoprotein expression increased dramatically when the cultures were held without passage for extended periods. The secretion of a number of plasma proteins was documented by metabolic labeling, immunoprecipitation, and gel analysis. The major plasma proteins detected were alpha-1-antitrypsin, alpha-fetoprotein, transthyretin, beta-2 microglobulin, and plasminogen, with lower levels of transferrin and complement C4 released. Apolipoproteins B, E, and A1 were secreted in high levels as well and were found in the form of lipoprotein particles. Time course experiments on the synthesis of apolipoproteins E and A1 indicated that, as with alpha-fetoprotein, the level of synthesis increased substantially when the cultures were held without passage. The results indicate that these yolk sac carcinoma cells display a protein expression profile similar to that observed for the human yolk sac, and the possibility that the cells may have the potential to differentiate is discussed.

Apolipoproteins↗
PubMed1990

Interaction of human embryonal carcinoma cells and differentiated derivatives in vitro with simian virus 40, human adenovirus type 7, or PARA.

Polyclonal antibodies were used to assay human embryonal carcinoma (EC), differentiating EC, yolk sac carcinoma, and teratoma cells for expression of viral early antigen (T-Ag) after infection with simian virus 40 (SV40). Cells of four EC lines were induced to differentiate by cultivation at low density or by exposure to retinoic acid or dimethyl sulfoxide. After infection with SV40, T-Ag was expressed by 1%, or less, of the cells (presumed to be differentiated derivatives) in only some EC cultures whereas the antigen was synthesized by a significant percentage of the yolk sac carcinoma, teratoma, and differentiating EC cells. Also, viral late proteins were produced by EC cells infected with human adenovirus type 7 (Ad7), and SV40 T-Ag was expressed by EC cells after infection with PARA, which is an Ad7-SV40 hybrid virus containing the SV40 T-Ag sequence controlled by Ad7 late regulatory sequences. Thus, T-Ag is not synthesized by the parental EC cells infected with SV40, but it is expressed in cultures of infected differentiated derivatives. The EC cells produce T-Ag, however, when expression of the viral protein is controlled by the Ad7 regulatory sequences in PARA particles. These results demonstrate that expression of T-Ag after infection with SV40 is an indicator of EC cell differentiation and also raise the possibility that, as in mouse EC cells infected with the virus, the SV40 regulatory sequences controlling T-Ag synthesis are not active in human EC cells.

Adenoviruses, Human↗
PubMed1990

Predictors of smoking behavior change 6 and 18 months after individual counseling during periodic health examinations.

Predictors of smoking behavior change were examined in a randomized controlled trial of individualized smoking cessation counseling delivered by a smoking cessation counselor during periodic health examination. Self-reports of not smoking at 6 and 18 months and attempts to quit were greater, but not significantly so, in the intervention group compared with the usual care group. There was no difference between the intervention group and the usual care group in reported continuous abstinence. Multivariate analysis showed that longer periods of abstinence in the past and having smoking identified as the main problem were important predictors of subsequent quitting. Having fewer other smokers in the household, stronger intentions to stop smoking in the next month, and being in the intervention group were also significant predictors of abstinence at 6 months, but not at 18 months. Those who had tried to quit by 6 months and 18 months were more likely to be in the intervention group, to have greater motivation to stop smoking, and to have more problems of daily living. Supplementing physician's advice with individualized smoking cessation counseling during health maintenance examinations was associated with a greater short-term quit rate and more quit attempts over 18 months than physician advice alone, but did not influence continuous abstinence from cigarettes over this time.

Attitude to Health↗
PubMed1990

Cellular oncogenes in human teratocarcinoma cell lines.

We have analysed, by Northern blots, the expression of 14 cellular oncogenes in nine cell lines established from human teratocarcinomas. All lines expressed considerable amounts of p53, c-Ki-ras2, c-Ha-ras1, c-raf1, N-myc, and c-fos. Low level expression of c-myc was detected in some lines. Southern blot experiments revealed no amplification or rearrangement of the c-Ki-ras2, N-myc or c-fos genes. Using a rapid dot-blot screening procedure, based on a combination of in-vitro amplification of ras-specific sequences and oligonucleotide hybridization, we could detect no activation of Ha-ras or Ki-ras or any unexpressed N-ras sequences secondary to a point mutation at codons 12, 13, or 61.

Blotting, Northern↗
PubMed1989

Smoking cessation counseling during periodic health examinations.

Periodic health examinations are an excellent opportunity to counsel smokers to quit. The impact of a specialized smoking cessation counselor on the smoking behavior of patients having periodic health examinations was studied in a general internal medicine practice. One hundred fifty-five smokers having periodic health examinations were randomly assigned to a control group who received usual physician advice or an intervention group who received usual physician advice and two counseling sessions with a smoking cessation counselor. The two groups were similar in all demographic variables, smoking-related baseline variables, and baseline levels of motivation and intention to quit smoking. The smoking status of 97% of the subjects was assessed 6 months later. In the intervention group, 46% made quit attempts and 19% quit, compared with 34% and 12%, respectively, in the control group. Intervention-group smokers made more quit attempts (mean +/- SD, 5.0 +/- 2.5 vs 1.8 +/- 0.2) and had a greater reduction in daily cigarette use (8.4 +/- 1.5 vs 3.5 +/- 1.3). Of the 74% of smokers with higher levels of motivation to quit smoking, more intervention-group smokers attempted to quit (70.8% vs 45.5%) and succeeded in quitting at the 6-month follow-up (27.1% vs 10.9%). Periodic health examinations are an excellent opportunity to counsel smokers to quit, especially those smokers with higher levels of motivation to quit smoking.

Adult↗
PubMed1987

Jejunal ulceration and stricture due to wax-matrix potassium chloride tablets and amitriptyline.

A 68-year-old woman presented with abdominal distention of several weeks duration and an acute small bowel obstruction. For several years she had been prescribed amitriptyline 150 mg/d, L-thyroxine 100 micrograms/d, and digoxin 0.25 mg/d. For the previous year she had been taking hydrochlorothiazide 50 mg/d and wax-matrix KCl 20 mEq/d for hypertension. At surgery a "napkin-ring" stricture of the midjejunum was found. It had microscopic features consistent with KCl local toxicity. It is speculated that delayed gastrointestinal motility secondary to amitriptyline predisposed this patient to wax-matrix KCl toxicity and that this potential side effect be considered when prescribing wax-matrix KCl.

Aged↗
PubMed1986

Using medical records for older patient education in ambulatory practice.

The effectiveness of sharing medical records in improving physician-older patient communication was evaluated in 203 ambulatory chronically ill older patients (mean age, 70.1 years) by a randomized controlled trial. Ninety-five experimental group patients received copies of their physicians' progress notes 1 week after their last office visit, and 108 control patients did not. After 1-2 weeks, knowledge of health problems, medication, and nonmedication treatments was assessed by interview. Experimental group patients knew 74.1% of their health problems, compared with 64.1% in the control groups (P less than 0.05). There was no difference in knowledge of medications or adherence to medication regimens. Experimental group patients displayed higher treatment knowledge scores than control group patients (P less than 0.01). Less-educated patients showed greater adherence to nonmedication treatments. Shared medical records can enhance physician-older patient communication about health problems and nonmedication treatments, but they do little to enhance medication knowledge or adherence to medication regimens.

Aged↗
PubMed1984

Differentiation potential of human embryonal carcinoma cell lines.

We have established 17 embryonal carcinoma (EC) cell lines from human testicular germ cell tumors by using three different methods of in vitro cultivation. Cultures of only three of these cell lines, and of clones derived from two of them, differentiate extensively when the cells are seeded at low density. A comparison is presented of the results obtained with the three methods used to establish and maintain these cell lines, and some properties of the three pluripotential EC lines are summarized.

Cell Line↗
PubMed1984

Production of virions with retrovirus morphology by human embryonal carcinoma cells in vitro.

Embryonal carcinoma (EC) cell lines established from human testicular germ-cell tumours produce, at low frequency, virions morphologically identical to type C retroviruses that have been observed by other workers in human placental tissues. The virus particles are formed while budding from the cell surface, and their numbers are increased by inducing the EC cells with 5-iodo-2'-deoxyuridine and dexamethasone. Assays for RNA-dependent DNA polymerase (reverse transcriptase) associated with purified virions suggested a low level of activity. In addition, another type of virus is occasionally produced by induced cells of three EC lines. These particles also form during the process of budding from the cell surface, but they have surface projections (spikes). Extracellular spiked virions frequently are pleomorphic, with a condensed, eccentric nucleoid, and thus morphologically resemble type B retroviruses. No virions of either type were detected with or without induction in cultures of differentiated EC cells or in cultures of yolk sac carcinoma or teratoma cells, both of which are considered malignant but differentiated derivatives of EC cells. The lack of virion production by these differentiated cells suggests developmental regulation of virus replication.

Cell Line↗