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Biomedical subjects

C M West

Publications and source records attributed to C M West.

At least 73 records · Page 4Linked to original sources
PubMed1997

A mortality study of employees of the nuclear industry in Oak Ridge, Tennessee.

An analysis was conducted of 27,982 deaths among 106,020 persons employed at four Federal nuclear plants in Oak Ridge, Tennessee, between 1943 and 1985. The main objectives were to extend the evaluation of the health effects of employment in the nuclear industry in Oak Ridge to include most workers who were omitted from earlier studies, to compare the mortality experience of workers among the facilities, to address methodological problems that occur when individuals employed at more than one facility are included in the analysis, and to conduct dose-response analyses for those individuals with potential exposure to external radiation. All-cause mortality and all-cancer mortality were in close agreement with national rates. The only notable excesses occurred for white males for lung cancer [standardized mortality ratio (SMR) = 1.18, 1,849 deaths] and non-malignant respiratory disease (SMR = 1.12, 1,568 deaths). A more detailed analysis revealed substantial differences in death rates among workers at the Oak Ridge plants. Evaluation of internally adjusted log SMRs using Poisson regression showed that workers employed only at Tennessee Eastman Corporation or K-25 and at multiple facilities had higher death rates than similar workers employed only at X-10 or Y-12, and that the differences were primarily due to non-cancer causes. Analysis of selected cancer causes for white males indicated large differences among the workers at the different facilities for lung cancer, leukemia and other lymphatic cancer. Dose-response analyses for external penetrating radiation were limited to a subcohort of 28,347 white males employed at X-10 or Y-12. Their collective recorded dose equivalent was 376 Sv. There was a strong "healthy worker effect" in this subcohort-all-cause SMR = 0.80 (4,786 deaths) and all-cancer SMR = 0.87 (1,134 deaths). Variables included in the analyses were age, birth cohort, a measure of socioeconomic status, length of employment, internal radiation exposure potential and facility. For external radiation dose with a 10-year lag, the excess relative risk was 0.31 per Sv (95% CI = -0.16, 1.01) for all causes and 1.45 per Sv (95% CI = 0.15, 3.48) for all cancer. The estimated excess relative risk for leukemia was negative but imprecisely determined. A preliminary dose adjustment procedure was developed to compensate for missing dose but not other dosimetry errors. Results of the analyses using the adjusted doses suggest that the effect of missing dose is an upward bias in dose-response coefficients and test statistics.

Dose-Response Relationship, Radiation↗
PubMed1996

Purification and characterization of an alpha1,2,-L-fucosyltransferase, which modifies the cytosolic protein FP21,from the cytosol of Dictyostelium.

A novel fucosyltransferase (cFTase) activity has been enriched over 10(6)-fold from the cytosolic compartment of Dictyostelium based on transfer of [3H]fucose from GDP-[3H]fucose to Galbeta1,3 GlcNAc beta-paranitrophenyl (paranitrophenyl-lacto-N-bioside or pNP-LNB). The activity behaved as a single component during purification over DEAE-, phenyl-, Reactive Blue-4-, GDP-adipate-, GDP-hexanolamine-, and Superdex gel filtration resins. The purified activity possessed an apparent Mr of 95 X 10(3), was Mg2+-dependent with a neutral pH optimum, and exhibited a Km for GDP-fucose of 0.34 microM, a Km for pNP-LNB of 0.6 mM, and a Vmax for pN-P-LNB of 620 nmol/min/mg protein. SDS-polyacrylamide gel electrophoresis analysis of the Superdex elution profile identified a polypeptide with an apparent Mr of 85 X 10(3), which coeluted with the cFTase activity and could be specifically photolabeled with the donor substrate inhibitor GDP-hexanolaminyl-azido-125I-salicylate. Based on substrate analogue studies, exoglycosidase digestions, and co-chromatography with fucosylated standards, the product of the reaction with pNP-LNB was Fucalpha1, 2Galbeta1,3GIcNAcbeta-pNP. The cFTase preferred substrates with a Galbeta1,3linkage, and thus its acceptor substrate specificity resembles the human Secretor-type alpha1,2- FTase. Afucosyl isoforms of the FP21 glycoprotein, GP21-I and GP21-II, were purified from the cytosol of a Dictyostelium mutant and found to be substrates for the cFTase, which exhibited an apparent K(m) of 0.21 microM and an apparent V(max) of 460 nmol/min/mg protein toward GP21-II. The highly purified cFTase was inhibited by the reaction products Fucalpha1,2Galbeta1,3GlcNAcbeta-pNP and FP21-II. FP21-I and recombinant FP21 were not inhibitory, suggesting that acceptor substrate specificity is based primarily on carbohydrate recognition. A cytosolic location for this step of FP21 glycosylation is implied by the isolation of the cFTase from the cytosolic fraction, its high affinity for its substrates, and its failure to be detected in crude membrane preparations.

Amino Acid Sequence↗
PubMed1996

SP75 is encoded by the DP87 gene and belongs to a family of modular Dictyostelium discoideum outer layer spore coat proteins.

Highly purified spore coats of Dictyostelium discoideum each contained about 5 x 10(6) protein molecules as determined by amino acid composition analysis. By two-dimensional gel electrophoresis the coats were found to contain nine major-abundance and numerous minor protein species, most of which were highly enriched relative to the adjacent interspore matrix. Protein was nearly quantitatively eluted by denaturants and 2-mercaptoethanol, showing that it was not irreversibly cross-linked. Because a reducing agent is required together with denaturants to elute most proteins if their free thiol groups have been prealkylated, it was concluded that the D. discoideum spore coat proteins are disulfide cross-linked into the matrix. One major coat protein, SP75, was partially sequenced and found to be encoded by the previously identified DP87 gene; this finding was supported by additional physical, genetic, biochemical and microscopic evidence. The five major proteins for which genes have been cloned were associated with the outer layer of the coat. In coats missing one or more of four of these proteins as a result of gene disruption, there were physical changes but, with one exception, the other major coat proteins appeared to be incorporated normally. Sequence analysis showed that these five outer layer coat proteins are homologous and consist of alternating sequence motifs related to epithelial mucin repeats, basic proline repeats found in salivary acidic proline-rich proteins, the NH2-terminal subdomain of epidermal growth factor modules and other cysteine repeats. Based on these and other observations, outer layer coat proteins are predicted to organize indeterminately to form a cell surface microenvironment supportive of cellulose morphogenesis during spore coat formation.

Amino Acid Sequence↗
PubMed1996

Assessment of light scatter by nucleoids as a rapid predictive assay of radiosensitivity.

A study has been made of the practicality of using the assay of light scatter by nucleoids as a rapid predictive test of cellular radiosensitivity. With this technique the effect of irradiation on DNA organization is measured using flow cytometry after staining irradiated nucleoids with a high concentration of ethidium bromide. Damaged nucleoids fail to respond to the ethidium bromide-induced contraction and scatter more forward-angle light than less damaged nucleoids. Seventeen different cell lines were assessed using a single lysis condition and radiation dose. Significant differences in the levels of radiation-induced forward-angle light scatter by nucleoids were seen between CHO cells and cells of two radiosensitive mutant cell lines (xrs-6, EM9), and between cells of two ovarian carcinoma lines that showed marked differences in radiosensitivity measured using a clonogenic assay. However, other cell lines which differed in clonogenic radiosensitivity showed similar forward-angle light scatter by nucleoids. When all 17 cell lines were included in the analysis, there was no correlation between measurements of radiosensitivity by assays of clonogenicity and light scatter by nucleoids. In addition, although intraexperimental variation was small, the level of interexperimental variability was only slightly smaller (coefficient of variation of 13%) than the degree of heterogeneity observed between the different cell lines (coefficient of variation of 16%). These findings support the notion for a role of nuclear structure as a determinant of intrinsic radiosensitivity for some cell lines but suggest that for others there must be additional, more dominant factors.

Animals↗
PubMed1995

Characterization of FP21, a cytosolic glycoprotein from Dictyostelium.

FP21 is a glycoprotein which, when tracked by radioactivity in its fucosyl moiety, was previously detected in the cytosol of Dictyostelium cells after cell fractionation. This compartmentalization is confirmed by SDS-polyacrylamide gel electrophoresis/Western blotting of cell fractions using three different antibodies. Although a substantial fraction of FP21 is also detected in the particulate fraction using these new antibodies, particulate FP21 is released by disrupting protein-protein interactions, but not membrane disruption. Since purified FP21 is susceptible to aggregation, and purified nuclei do not contain FP21, particulate FP21 is also part of the cytosol. Additional compositional and structural information provides strong evidence that FP21 does not at any time traverse the rough endoplasmic reticulum. First, cDNAs spanning the entire coding region of the FP21 gene predict no hydrophobic motifs expected to promote membrane insertion, but do predict an NH2-terminal coiled coil domain which could explain aggregation. Second, monosaccharide composition analysis of the predominant glycoform of FP21 yields 2 mol of galactose, 1 mol of xylose, and 1 mol of fucose/mol of polypeptide; FP21 from a fucosylation-defective mutant contains 1 additional mol of xylose in place of fucose. Thus the N-glycosylation sequon present in FP21 is not utilized by oligosaccharyl transferase, which resides in the rough endoplasmic reticulum. These findings indicate that nascent FP21 remains in the cytosol after synthesis and is therefore glycosylated by unusual cytosolic xylosyl-, galactosyl-, and fucosyltransferases.

Amino Acid Sequence↗
PubMed1995

The intrinsic radiosensitivity of cervical carcinoma: correlations with clinical data.

PURPOSE: The aims of the work were to study the intrinsic radiosensitivity of tumor biopsies from patients with cervical carcinoma and to correlate the data with information on patient age, disease stage, differentiation status, tumor volume, and tumor ploidy. METHODS AND MATERIALS: Radiosensitivity was assessed for 145 tumors in vitro as surviving fraction at 2 Gy (SF2) using a clonogenic assay. RESULTS: Although the clonogens in tumors classified as Stage I or II tended to be more radiosensitive than in Stage III or IV disease, the difference was not statistically significant (p > 0.15). There was also no significant difference in the intrinsic radiosensitivity of well, moderately, or poorly differentiated tumors or between squamous cell carcinoma and adenocarcinoma (p > 0.53). There was no correlation between patient age and tumor radiosensitivity (p = 0.49). Large volume (> or = 4 cm) disease was more radioresistant than small volume (< 4 cm) disease, but the difference was not significant (p = 0.08). Finally, diploid tumors tended to be more radioresistant than aneuploid tumors (p = 0.07). CONCLUSION: The intrinsic radiosensitivity of cervix tumors is independent of disease stage, tumor grade, and patient age. Weak trends, however, were observed of increased tumor radioresistance for large volume disease and diploid tumors, suggesting that tumor SF2 may not be a completely independent parameter.

Adenocarcinoma↗
PubMed1995

Serum tumour markers in carcinoma of the uterine cervix and outcome following radiotherapy.

A study was made of the prognostic value of measurements of pretreatment serum marker levels in patients with carcinoma of the uterine cervix undergoing radiotherapy. The markers studied were carcinoma antigen 125 (CA125), squamous cell carcinoma antigen (SCC) and tissue polypeptide antigen (TPA). The levels of all three markers increased with disease stage. In a univariate analysis stratifying patients according to either median values or cut-off levels representing the top of the normal range, pretreatment levels predicted patient survival (follow-up times 1-4 years). In a multivariate analysis, disease stage was the most important prognostic variable and, after allowing for stage, only CA125 was a significant independent predictor of treatment outcome. These data suggest that, in carcinoma of the cervix treated with radiotherapy, pretreatment measurements of CA125, but not SCC and TPA, may have a role to play in defining prognosis.

Antigens, Neoplasm↗
PubMed1995

Relationships between the cytotoxic effects of restriction endonucleases and radiation on mammalian cells.

Wild-type Chinese hamster ovary (CHO) cells, a radiosensitive mutant CHO line (xrs6), and two human cervical carcinoma cell lines, MS751 and ME180, differ in sensitivity to ionizing radiation with surviving fractions at 2 Gy (SF2) of 0.84, 0.06, 0.90 and 0.24 respectively. Restriction endonucleases (REs) were introduced into the cells by treatment with streptolysin O (SLO) and the effects of this on clonogenic cell survival were compared. A comparison was made of REs inducing either blunt- (AluI) or cohesive-ended (Sau3AI) double-strand breaks. Whilst MS751 cells were resistant to the effects of both REs, AluI caused significantly greater cell killing than Sau3AI in the other three lines (p < 0.05 for all). Both ME180 and xrs6 were significantly more sensitive to REs than their radioresistant counterparts, MS751 and CHO (p < 0.05 for both). In order to investigate the effect of DNA methylation on dsb induction, the isoschizomers MspI and HpaII (cohesive-ended dsb inducers) were introduced into the cell lines. Both REs recognize the same sequence but HpaII cannot cleave if the internal cytosine is methylated. MS751 was also resistant to the effects of both of these enzymes and MspI was more cytotoxic than HpaII in the other three lines (p < 0.03 for all). The differential sensitivity to the two REs was more marked in the radiosensitive cell lines, suggesting that there may be a greater degree of DNA methylation in radiosensitive cells. The variation in sensitivities to REs between the cell lines could not be explained in terms of differences in cell poration following SLO treatment because, although MS751 was resistant to SLO (25% of cells porated), the other three lines showed the same level of cell poration (98% of cells). With these four cell lines, there was a significant correlation between sensitivity to RE and radiosensitivity for AluI, Sau3AI and MspI but not for HpaII.

Animals↗
PubMed1995

A comparison of the radiosensitivity of lymphocytes from normal donors, cancer patients, individuals with ataxia-telangiectasia (A-T) and A-T heterozygotes.

The aim was to determine whether peripheral blood lymphocytes can be used retrospectively to detect hypersensitivity to radiation in breast cancer patients who had exhibited severe reactions to radiotherapy. Blood samples were obtained from patients who developed both acute and late complications. For comparison, samples were also taken from a group of normal individuals, ataxia-telangiectasia (A-T) patients, A-T gene carriers and breast cancer patients previously treated with radiotherapy who failed to develop treatment-related complications. Radiosensitivity was assessed using a limiting dilution clonogenic assay following both high (HDR) and low (LDR) dose-rate irradiation. Following HDR irradiation, only lymphocytes from individuals with A-T were significantly more radiosensitive than those from normal donors. In contrast, at LDR, lymphocytes from A-T heterozygotes and breast cancer over reactors were also, on average, more sensitive than those from normal donors. Lymphocytes from breast cancer patients treated with radiotherapy without developing complications showed no significant differences in radiosensitivity compared with normals. This work has shown that peripheral blood lymphocytes from cancer patients who suffered severe reaction to radiotherapy are, on average, more radiosensitive than those from normal donors, and suggests that lymphocytes may be useful in the future for the development of rapid predictive assays for normal tissue tolerance to radiotherapy.

Ataxia Telangiectasia↗
PubMed1995

Uranium dust exposure and lung cancer risk in four uranium processing operations.

We examined the relation between uranium dust exposure and lung cancer mortality among workers employed in four uranium processing or fabrication operations located in Missouri, Ohio, and Tennessee. Among workers who had at least 30 years of potential follow-up, we identified 787 lung cancer cases from death certificates and matched one control to each case. Health physicists estimated individual annual lung doses from occupational exposure primarily to insoluble uranium compounds, using contemporary monitoring data. With a 10-year lag, cumulative lung doses ranged from 0 to 137 centigrays (cGy) for cases and from 0 to 80 cGy for controls. Health physicists assigned annual external radiation doses to workers having personal monitoring records. Archivists collected smoking information from occupational medical records. Odds ratios for lung cancer mortality for seven cumulative internal dose groups did not demonstrate increasing risk with increasing dose. We found an odds ratio of 2.0 for those exposed to 25 cGy and higher, but the 95% confidence interval of 0.20 to 20 showed great uncertainty in this estimate. There was a suggestion of an exposure effect for workers hired at age 45 years or older. Further analyses for cumulative external doses and exposures to thorium, radium, and radon did not reveal any clear association between exposure and increased risk, nor did dichotomizing workers by facility.

Adult↗
PubMed1995

Lung dose estimates from air sampling and bioassay data--a comparison.

Occupational monitoring data are typically in the form of air samples or biological samples. Air samples are more frequently available and often have been used to characterize personnel exposure in epidemiological studies. Air samples that are not specific to individual employees are easier and cheaper to procure than biological samples such as urinalyses. However, the correlation between concurrent air samples and urinalyses has not always been found to be strong. The purpose of this paper is to compare internal radiation doses for uranium workers estimated from air sample results with those estimated from urine sample results. The comparison was made on results associated with individuals who worked in a uranium processing and fabrication facility between 1950 and 1956. Independent lung dose estimates were made for individuals for whom both types of data were available for periods of 300-365 d. Plots of the data and statistical analyses failed to show evidence of correlation of any practical significance between the data generated by the two methods. A number of unquantifiable variables were enumerated for both types of estimates. It is concluded that within this study (1) only minimal correlation was demonstrable between lung doses based on air monitoring and doses based on urinalysis data because of the number of such variables affecting the measurements; and (2) general air data would not be the most useful measure of exposure upon which to base lung dose estimates.

Air Pollutants, Radioactive↗
PubMed1995

Immunochemical, genetic and morphological comparison of fucosylation mutants of Dictyostelium discoideum.

Mutations in three loci in Dictyostelium discoideum which affect fucosylation are described. Mutations in two of these loci resulted in the simultaneous loss of two separate carbohydrate epitopes. The GA-X epitope, which was competed by L-fucose, was absent in strains carrying a modC354, modD352 or modE353 mutation. These strains exposed a new carbohydrate epitope, competed by N-acetylglucosamine, and the size of several glycoproteins was reduced. A second epitope (GA-XII) was also absent in strains carrying the modC354 or modE353 mutations, reducing the size of the glycoprotein which normally expresses it. Fucose content was reduced in the three mutants, suggesting that each mutation affected a separate step in fucosylation. The lesions did not appear to inhibit synthesis of the underlying carbohydrate, because detergent extracts of mutant vesicles were more active than normal vesicles at transferring [14C]fucose from GDP-[14C]fucose to endogenous acceptor species. The modD352 and modE353 mutant strains incorporated exogenous [3H]fucose poorly, suggesting that lesions in the modD and modE genes interfere with the biosynthesis of fucoconjugates downstream from the previously described GDP-fucose synthesis defect of the modC mutation. Intact modE353 mutant vesicles were relatively inefficient in in vitro assays, suggesting a global fucosylation defect (which is consistent with the loss of both glycoantigens, GA-X and GA-XII, in this mutant). Finally, the modC354 mutation led to delayed accumulation of slime sheath in vitro. The three genetic loci define a fucosylation pathway in D. discoideum comprising defined biochemical steps which contribute to multicellular morphogenesis in this organism.

Animals↗
PubMed1994

Identification of a new spore coat protein gene in the cellular slime mold Dictyostelium discoideum.

Genomic DNA encoding the prespore cell-specific PL3 cDNA was cloned and sequenced, revealing that the gene consists of three exons separated by short 100-bp introns. The single long open reading frame predicts a primary translation product of 70 kDa after removal of a cleavable signal peptide, two-thirds of which consists of four kinds of amino acid repeat elements, including two found in other spore coat proteins. The 85-kDa PL3 protein synthesized in vivo accumulates specifically in regulated secretory vesicles of prespore cells (prespore vesicles), as determined microscopically using antibody against a PL3 gene fusion product expressed in Escherichia coli. The protein later accumulates extracellularly in the spore coat, which is formed during sporulation, as determined ultrastructurally and by Western blot analysis of SDS-PAGE gels. In addition to its high proportion of repeat elements, the PL3 protein has the following properties which distinguish it from other spore coat proteins: (1) it is located at the outer extent of the middle layer, beneath the outer layer, (2) its dissociation from the coat requires the presence of protein denaturants and reducing agents at elevated temperature, and (3) a large proportion of the protein is not dissociated from the coat even under these conditions, as determined by ultrastructural analysis of the extracted coat. The PL3 protein may contribute to the structure of the coat at the interface between the middle, cellulosic layer and the outer, electron-dense, proteinaceous layer.

Amino Acid Sequence↗
PubMed1994

Effects of 4-hydroxytamoxifen and a novel pure antioestrogen (ICI 182780) on the clonogenic growth of human breast cancer cells in vitro.

We have investigated the effects on breast cancer cell growth of 4-hydroxytamoxifen (4OHT), a conventional antioestrogen with agonist activity, and 7 alpha-[9-(4,4,5,5,5-pentafluoropentylsulphinyl)nonyl]oestra- 1,3,5,(10)- triene-3,17 beta-diol (ICI 182780), a novel, pure antioestrogen, using established human breast cancer cell lines and cancer cells obtained directly from breast cancer patients with malignant pleural effusions who had relapsed on tamoxifen. The effects of the two agents were assessed using the Courtenay-Mills clonogenic assay, which measures the growth of single cancer cells as colonies suspended in soft agar. The standard assay was modified by the use of defined serum- and phenol red-free growth medium. The growth of oestrogen receptor (ER)-positive MCF-7 cells in the assay was oestrogen responsive. Both antioestrogens inhibited the stimulatory effects of 1 nM oestradiol, but ICI 182780 caused significantly greater inhibition than 4OHT at 0.1-1.0 microM concentrations. In the absence of oestradiol, 4OHT but not ICI 182780 caused significant stimulation of colony formation at low (0.01-1.00 nM) concentrations. Neither antioestrogen had any effects on colony formation by the ER-negative Hs578T cell line. Successful colony formation was obtained in primary cultures from six out of eight malignant effusions. Colony formation was significantly stimulated by 0.1 nM oestradiol in four cases and by 10 nM 40HT in two cases. In contrast, ICI 182780 exhibited no intrinsic stimulatory activity and significantly inhibited both oestradiol- and 4OHT-stimulated cell growth. We conclude that the agonist activity of 4OHT and other conventional antioestrogens may cause treatment failure in some patients by stimulating breast cancer cell growth. The new, pure antioestrogen ICI 182780 is a more potent oestrogen antagonist than 4OHT and exhibits no growth-stimulatory activity. This agent may therefore offer therapeutic advantages over conventional antioestrogens in patients with advanced breast cancer and may be effective after conventional agents have failed.

Adult↗