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Biomedical subjects

R M Ray

Publications and source records attributed to R M Ray.

At least 37 records · Page 2Linked to original sources
PubMed2000

Putrescine does not support the migration and growth of IEC-6 cells.

The migration of IEC-6 cells is inhibited when the cells are depleted of polyamines by inhibiting ornithine decarboxylase with alpha-difluoromethylornithine (DFMO). Exogenous putrescine, spermidine, and spermine completely restore cell migration inhibited by DFMO. Because polyamines are interconverted during their synthesis and catabolism, the specific role of individual polyamines in intestinal cell migration, as well as growth, remains unclear. In this study, we used an inhibitor of S-adenosylmethionine decarboxylase, diethylglyoxal bis(guanylhydrazone)(DEGBG), to block the synthesis of spermidine and spermine from putrescine. We found that exogenous putrescine does not restore migration and growth of IEC-6 cells treated with DFMO plus DEGBG, whereas exogenous spermine does. In addition, the normal distribution of actin filaments required for migration, which is disrupted in polyamine-deficient cells, could be achieved by adding spermine but not putrescine along with DFMO and DEGBG. These results indicate that putrescine, by itself, is not essential for migration and growth, but that it is effective because it is converted into spermidine and/or spermine.

Actins↗
PubMed1999

Polyamine depletion alters the relationship of F-actin, G-actin, and thymosin beta4 in migrating IEC-6 cells.

The cause of reduced migration ability in polyamine-deficient cells is not known, but their actin cytoskeleton is clearly abnormal. We depleted polyamines with alpha-difluoromethylornithine (DFMO) in migrating cells with or without stimulation by epidermal growth factor (EGF) and investigated filamentous (F-) actin, monomeric (G-) actin, and thymosin beta4 (Tbeta4), using immunofluorescent confocal microscopy, DNase assay, and immunoblot analysis. DFMO reduced F-actin in the cell interior, increased it in the cell cortex, redistributed G-actin, and increased nuclear staining of Tbeta4. However, DFMO did not affect the amount of Tbeta4 mRNA. EGF caused a rapid increase in the staining of F-actin in control cells, but DFMO prevented this response to EGF. Despite the visible changes shown by immunocytochemistry, statistically significant changes in the amount of either actin isoform or of total actin did not occur. We propose that DFMO reduces migration by interfering with the sequestration of G-actin by Tbeta4 and the association of F-actin with activated EGF receptors.

Actins↗
PubMed1999

Polyamine depletion arrests cell cycle and induces inhibitors p21(Waf1/Cip1), p27(Kip1), and p53 in IEC-6 cells.

The polyamines spermidine and spermine and their precursor putrescine are intimately involved in and are required for cell growth and proliferation. This study examines the mechanism by which polyamines modulate cell growth, cell cycle progression, and signal transduction cascades. IEC-6 cells were grown in the presence or absence of DL-alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase, which is the first rate-limiting enzyme for polyamine synthesis. Depletion of polyamines inhibited growth and arrested cells in the G1 phase of the cell cycle. Cell cycle arrest was accompanied by an increase in the level of p53 protein and other cell cycle inhibitors, including p21(Waf1/Cip1) and p27(Kip1). Induction of cell cycle inhibitors and p53 did not induce apoptosis in IEC-6 cells, unlike many other cell lines. Although polyamine depletion decreased the expression of extracellular signal-regulated kinase (ERK)-2 protein, a sustained increase in ERK-2 isoform activity was observed. The ERK-1 protein level did not change, but ERK-1 activity was increased in polyamine-depleted cells. In addition, polyamine depletion induced the stress-activated protein kinase/c-Jun NH2-terminal kinase (JNK) type of mitogen-activated protein kinase (MAPK). Activation of JNK-1 was the earliest event; within 5 h after DFMO treatment, JNK activity was increased by 150%. The above results indicate that polyamine depletion causes cell cycle arrest and upregulates cell cycle inhibitors and suggest that MAPK and JNK may be involved in the regulation of the activity of these molecules.

Animals↗
PubMed1999

Interaction of asparagine and EGF in the regulation of ornithine decarboxylase in IEC-6 cells.

Our laboratory has shown that asparagine (ASN) stimulates both ornithine decarboxylase (ODC) activity and gene expression in an intestinal epithelial cell line (IEC-6). The effect of ASN is specific, and other A- and N-system amino acids are almost as effective as ASN when added alone. In the present study, epidermal growth factor (EGF) was unable to increase ODC activity in cells maintained in a salt-glucose solution (Earle's balanced salt solution). However, the addition of ASN (10 mM) in the presence of EGF (30 ng/ml) increased the activity of ODC 0.5- to 4-fold over that stimulated by ASN alone. EGF also showed induction of ODC with glutamine and alpha-aminoisobutyric acid, but ODC induction was maximum with ASN and EGF. Thus the mechanism of the interaction between ASN and EGF is important for understanding the regulation of ODC under physiological conditions. Therefore, we examined the expression of the ODC gene and those for several protooncogenes under the same conditions. Increased expression of the genes for c-Jun and c-Fos but not for ODC occurred with EGF alone. The addition of ASN did not further increase the expression of the protooncogenes, but the combination of EGF and ASN further increased the expression of ODC over that of ASN alone. Western analysis showed no significant difference in the level of ODC protein in Earle's balanced salt solution, ASN, EGF, or EGF plus ASN. Addition of cycloheximide during ASN and ASN plus EGF treatment completely inhibited ODC activity without affecting the level of ODC protein. These results indicated that 1) the increased expression of protooncogenes in response to EGF is independent of increases in ODC activity and 2) potentiation between EGF and ASN on ODC activity may not be due to increased gene transcription but to posttranslational regulation and the requirement of ongoing protein synthesis involving a specific factor dependent on ASN.

Animals↗
PubMed1998

Molybdate-dependent transcription of hyc and nar operons of Escherichia coli requires MoeA protein and ModE-molybdate.

In Escherichia coli, ModE-molybdate, a repressor of modABCD operon (molybdate transport), was previously shown to be an additional transcriptional activator of hyc operon (formate hydrogenlyase) and narGHJI operon (respiratory nitrate reductase). However, in a modE mutant, both operons were expressed at about 50% of the wild-type level in a molybdate-dependent manner. This ModE-independent, molybdate-dependent, expression of hyc, narG and narK operons required MoeA protein. An E. coli modE, moeA double mutant failed to produce formate hydrogenlyase or respiratory nitrate reductase activity irrespective of the growth medium. Tungstate substituted for molybdate in the activation of transcription of hyc and nar operons by ModE could not replace molybdate for MoeA-dependent expression. It is proposed that the MoeA-catalyzed product, an activated form of molybdate, interacts with a transcriptional activator/regulator other than ModE and regulates hyc and nar operons.

Bacterial Proteins↗
PubMed1998

Physiological and genetic analyses leading to identification of a biochemical role for the moeA (molybdate metabolism) gene product in Escherichia coli.

A unique class of chlorate-resistant mutants of Escherichia coli which produced formate hydrogenlyase and nitrate reductase activities only when grown in medium with limiting amounts of sulfur compounds was isolated. These mutants failed to produce the two molybdoenzyme activities when cultured in rich medium or glucose-minimal medium. The mutations in these mutants were localized in the moeA gene. Mutant strains with polar mutations in moeA which are also moeB did not produce active molybdoenzymes in any of the media tested. moeA mutants with a second mutation in either cysDNCJI or cysH gene lost the ability to produce active molybdoenzyme even when grown in medium limiting in sulfur compounds. The CysDNCJIH proteins along with CysG catalyze the conversion of sulfate to sulfide. Addition of sulfide to the growth medium of moeA cys double mutants suppressed the MoeA- phenotype. These results suggest that in the absence of MoeA protein, the sulfide produced by the sulfate activation/reduction pathway combines with molybdate in the production of activated molybdenum. Since hydrogen sulfide is known to interact with molybdate in the production of thiomolybdate, it is possible that the MoeA-catalyzed activated molybdenum is a form of thiomolybdenum species which is used in the synthesis of molybdenum cofactor from Mo-free molybdopterin.

Bacterial Proteins↗
PubMed1996

Oral contraceptives and invasive adenocarcinomas and adenosquamous carcinomas of the uterine cervix. The World Health Organization Collaborative Study of Neoplasia and Steroid Contraceptives.

Data from a hospital-based case-control study collected between 1979 and 1988 in 10 participating hospitals in eight countries were analyzed to determine whether use of combined oral contraceptives alters the risks of invasive adenocarcinomas and adenosquamous carcinomas of the uterine cervix. Information on prior use of oral contraceptives, suspected risk factors for cervical cancer, and history of cytologic screening was ascertained from interviews with 271 women with adenocarcinomas, 106 with adenosquamous carcinomas, and a large pool of hospitalized controls, from which 2,887 were matched to the cases included in this report. History of smoking and anogenital warts and blood specimens for measurement of herpes simplex and cytomegalovirus antibodies were obtained from subsets of these women, as was a sexual history from a subset of their husbands. The epidemiologic features and associations with oral contraceptives were similar for adenocarcinoma and adenosquamous carcinoma. For both types combined, risk increased with duration of oral contraceptive use, was highest in recent and current users, and declined with time since cessation of use. These trends in risk were strongest for cancers that occurred in women under age 35 years, and the association with risk was somewhat stronger for high compared with low progestin potency products. The strength of the observed relation with oral contraceptives was about the same as has been observed for invasive squamous cell cervical carcinomas. Women who have used oral contraceptives should be considered at increased risk of adenomatous cervical carcinomas.

Adenocarcinoma↗
PubMed1996

Prostitution, condom use, and invasive squamous cell cervical cancer in Thailand.

Cervical cancer is probably caused by a sexually transmitted agent. A case-control study was conducted in three hospitals in Thailand to investigate further the role of male sexual behavior, particularly regarding sexual contacts with prostitutes, in the development of this disease. Data were obtained from interviews with 225 married women with invasive squamous cell cervical carcinoma and 791 hospitalized controls, all of whom reported having only one sexual partner, and from interviews with their husbands. Risk of cervical cancer was strongly related to the women's husbands having visited prostitutes without using a condom when the husbands were less than 30 years old. A strong increasing trend in risk in relation to decreasing frequency of the husbands' condom use with prostitutes was observed, and a weaker increasing trend in risk with husbands' estimated lifetime total number of visits to prostitutes was found. The average latent period between the women's likely initial exposure to a sexually transmitted oncogenic agent and her diagnosis of invasive cervical cancer was about a quarter of a century. Regular use of condoms by customers of prostitutes could reduce the number of invasive cervical cancer cases in the general population of Thailand by at least one fourth.

Adult↗
PubMed1996

Repression of the Escherichia coli modABCD (molybdate transport) operon by ModE.

The modABC gene products constitute the molybdate-specific transport system in Escherichia coli. Another operon coding for two proteins which diverges from the modABCD operon has been identified. The first gene of this operon codes for a 262-amino-acid protein, designated ModE (28 kDa), and the second genes codes for a 490-amino-acid protein. ModF (54 kDa). The role of ModF has not yet been determined; however, mutations in modE depressed modABCD transcription even in the presence of molybdate, suggesting that ModE is a repressor. ModE, in the presence of 1 mM molybdate, repressed the production of plasmid-encoded ModA and ModB' proteins in an in vitro transcription-translation system. DNA mobility shift experiments confirmed that ModE binds to an oligonucleotide derived from the operator region of the modABCD operon. Further experimentation indicated that ModE binding to target DNA minimally requires an 8-bp inverted-repeat sequence, TAAC GITA. A highly conserved amino acid sequence, TSARNOXXG (amino acids 125 to 133), was identified in ModE and homologs from Azotobacter vinelandii, Haemophilus influenzae, Rhodobacter capsulatus, and Clostridium pasterianum. Mutants with mutations in either T or G of this amino acid sequence were isolated as "superrepressor" mutants. These mutant proteins repressed modABCD transcription even in the absence of molybdate, which implies that this stretch of amino acids is essential for the binding of molybdate by the ModE protein. These results show that molybdate transport in E. coli is regulated by ModE, which acts as a repressor when bound to molybdate.

Amino Acid Sequence↗
PubMed1995

Cervical carcinoma in situ and use of depot-medroxyprogesterone acetate (DMPA). WHO Collaborative Study of Neoplasia and Steroid Contraceptives.

The relationship of depot-medroxyprogesterone acetate (D-MPA) use to risk of cervical carcinoma in situ was investigated using data from a large multi-national, hospital-based case-control study. To avoid possible detection bias from Pap smear screening, final analyses were restricted to a subset of cases with symptoms at the time of their diagnosis of cervical carcinoma in situ. Relative to nonusers, the risk was elevated in women who had ever used DMPA and increased with duration of use. Decreasing trends in relative risk with times since first and last uses were observed in long-term users. Results from another portion of this same study did not show a relationship of invasive cervical cancer to DMPA use. These findings suggested that if DMPA increases the risk of cervical carcinoma in situ then either this is a reversible effect, or the cervical lesions induced by DMPA tend not to progress to invasive disease.

Adult↗
PubMed1995

Depot-medroxyprogesterone acetate (DMPA) and risk of invasive adenocarcinomas and adenosquamous carcinomas of the uterine cervix. WHO Collaborative Study of Neoplasia and Steroid Contraceptives.

A hospital-based case-control study was conducted in two hospitals in Bangkok, Thailand, and in one hospital each in Chiang Mai, Thailand, Mexico City, Mexico and Nairobi, Kenya. One purpose of this study was to determine whether the long-acting progestational contraceptive, depot-medroxyprogesterone acetate (DMPA), alters risk of invasive cervical carcinomas with adenomatous histological features. Information on prior use of DMPA, screening for cervical cancer, and the suspected risk factors for this disease was ascertained from interviews of 239 women with adenocarcinomas and 85 women with adenosquamous carcinomas, as well of from a large pool of controls, 2534 of whom were matched to the cases included in this report. For selected subsets of these women, a smoking history was also elicited, blood specimens were collected for measurement of antibodies against herpes simplex and cytomegalovirus, and information on sexual behavior was obtained from interviews of their husbands. The relative risk (and 95% confidence interval) of adenomatous cervical carcinomas in women who ever used DMPA was estimated to be 0.75 (0.51, 1.11). No trends in risk were observed with duration of DMPA use, times since first or last use, or age at first use. The results provide reassurance that use of DMPA for over four years does not enhance risk of adenomatous cervical carcinomas, and risk is not increased after a potential latent period of over 12 years since initial exposure.

Adenocarcinoma↗
PubMed1995

Combined oral contraceptives and risk of cervical carcinoma in situ. WHO Collaborative Study of Neoplasia and Steroid Contraceptives.

BACKGROUND: Although the possible influence of oral contraceptives on risk of cervical carcinoma in situ has been the subject of multiple prior investigations, the results have been inconsistent. METHODS: Data from a multinational, collaborative case-control study were analysed to investigate further this possible relationship. To assess potential screening bias, some statistical analyses were restricted to subgroups of cases with and without symptoms at the time of their diagnosis. RESULTS: Relative risk estimates in relation to various features of oral contraceptive use tended to be highest for asymptomatic disease, lowest for disease presenting with vaginal bleeding, and intermediate for disease presenting with other symptoms, suggesting the presence of a screening bias. In women with vaginal bleeding, who are least likely to have been detected by routine screening, no elevated risk of cervical carcinoma in situ was observed in relation to ever having used combined oral contraceptives, but there was an increased risk in users of over 60 months' duration. An increasing trend in risk with duration of use was most pronounced in these women who first used oral contraceptives in the past 5-10 years; and in women who used oral contraceptives for more than 60 months, risk declined with time since last use. CONCLUSION: These findings could reflect a reversible effect of long-term use of oral contraceptives at an intermediate stage in the carcinogenic process, or a non-causal relationship due to unidentified sources of bias or confounding.

Adult↗
PubMed1989

Monthly injectable steroid contraceptives and cervical carcinoma.

The World Health Organization Collaborative Study of Neoplasia and Steroid Contraceptives is a large multinational hospital-based case-control study of steroid contraceptives and gynecologic, hepatobiliary, and mammary neoplasms. Monthly injectable steroid contraceptives which contained the long-acting progestogen dihydroxyprogesterone acetofenide plus a shorter-acting estrogen (usually estradiol enanthate) were used by women in two of the countries (Chile and Mexico) from which data were collected. In preliminary analyses of data from Chile (1979-1983), a strong association was observed between use of these products and invasive cervical cancer. Therefore, three additional data sets from these two countries were analyzed in further detail for this report. Analyses of additional data from Chile on invasive cervical cancer (1983-1985) and cervical carcinoma in situ (1979-1986) and of data on invasive cervical cancer from Mexico (1979-1986) failed to confirm the initially observed association. The original finding was probably due to chance, but a causal interpretation cannot be confidently ruled out, and additional studies are warranted.

Algestone Acetophenide↗
PubMed1988

Oral contraceptives and cervical carcinoma in situ in Chile.

A case-control study of cervical carcinoma in situ was conducted in Santiago, Chile, to determine whether risk of this condition is altered by use of oral contraceptives. Responses to a standardized questionnaire were compared in 133 hospitalized cases and 254 age-matched controls selected from the same screening program through which the cases were detected. After controlling for the possible confounding influence of a variety of indices of sexual behavior, socioeconomic status, and prior cytological smears, no increase in risk was found in women who ever used oral contraceptives. No trend of increasing or decreasing risk was seen in relation to duration of use, up to more than 6 years of exposure, or with the passage of time from either initial or most recent exposure. An observed increase in risk in current users of oral contraceptives was not considered likely to represent a causal relationship.

Abortion, Spontaneous↗
PubMed1982

Chlamydia trachomatis and cervical neoplasia.

We tested 383 women with and 500 women without cervical neoplasia for antibodies against Chlamydia trachomatis or herpes simplex virus (HSV). Exposure to both agents was related to sexual activity, with the highest prevalence of antibodies found in women with more sex partners and who had first coitus at an earlier age. When subjects were matched for several risk factors (age, race, marital status, parity, number of sex partners, and history of venereal disease), a significant excess of antibodies against C trachomatis was found in cases as compared with control subjects (76.5% v 58.4%, respectively; n = 149). Because matched-pair analysis lost a substantial proportion of women with neoplasia (largely because they were older), linear logistic analysis was performed. This also showed an excess of antichlamydial antibody in cases, with an estimated odds ratio of approximately 2 for the association of antichlamydial antibody and the risk of being a case. Neither analysis found an excess of antibodies to HSV type 2 in cases.

Adolescent↗
PubMed1980

Interrelationships among subgroups of serum lipoproteins in normal human subjects.

Analytic ultracentrifugation of serum lipoproteins from 80 men and 54 women aged 27--66 was used to determine if specific segments of the high density (HDL), low density (LDL) and very low density (VLDL) lipoprotein schlieren curves could be defined so as to reveal significant correlations among them. Differences in correlations resulted in division of LDL into three subgroups based on flotation rate S(0)(f) 0--7, 7--12, and 12--20) and division of HDL into two subgroups F(0)(1.20) 0--1.5 and s--9). HDL of F(0)(1.20) 2--9 (designated HDL 2--9) correlated negatively with LDL of S(0)(f) 0--7 (LDL 0--7) for all groups, positively with LDL of S(0)(f) 7--12 except in women aged 27--46, and negatively with VLDL except in men aged 47--66. HDL of F1.20(0) 0--1.5 (HDL0-1.5) correlated positively with LDL 0-7 except in men aged 27--46 and with VLDL in all but older men. Some correlations were reduced to non-significant levels by controlling for LDL (0-7) or VLDL. Correlations of HDL and LDL flotation subgroups yielded no significant net correlation between total HDL and LDL. Total HDL was directly correlated with HDL (2-9) (r greater than 0.97) but not with HDL0-1.5. The foregoing suggests that decreased HDL represents reduced HDL2-9 and may be accompanied by increased LDL0-7 and VLDL. LDL0-7 may represent and "atherogenic" LDL subclass in part responsible for increased coronary risk associated with low HDL.

Adult↗
PubMed1979

Fecal bile acids in two Japanese populations with different colon cancer risks.

Some workers have associated fecal bile acids with colon cancer frequency. They suggest that the risk for colon cancer increases with a rise in the level of total and degraded fecal bile acids. The Japanese in Hawaii, who are at high risk for this cancer, had higher concentrations of deoxycholic acid (a degraded bile acid) in their fecal specimens than did the people in Akita, Japan, who are at low risk. However, the findings for the other bile acids were unremarkable or inconsistent. These data were suggestive, but not strongly supportive, of a relationship between fecal bile acid patterns and colon cancer risk.

Adult↗