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Biomedical subjects

D Roy

Publications and source records attributed to D Roy.

At least 181 records · Page 10Linked to original sources
PubMed1995

Mutations in DNA polymerase beta mRNA of stilbene estrogen-induced kidney tumors in Syrian hamster.

We report here the alteration(s) in the expression of the DNA repair gene, DNA polymerase beta, in kidney tumors induced by stilbene estrogen (diethylstilbestrol, DES). RT-PCR, slot blotting, and Northern blotting experiments revealed that expression of DNA polymerase beta (DNA pol beta) was several fold lower in stilbene-estrogen-induced kidney tumors than in age-matched controls. Several mutations were identified in DNA pol beta mRNA from DES-induced kidney tumors, but not in age-matched control kidney. The mutations in DNA pol beta mainly occurred in the catalytic domain of pol beta, and not in the DNA binding domain. All the mutations produced a stop codon at nucleotide 199 indicating that a protein of aberrant size may be synthesized. These data suggest that mutation of DNA pol beta coupled with attenuation in expression might compromise the DNA repair system. This in turn may allow a greater error rate during DNA repair and the accumulation of lesions in the genome.

Animals↗
PubMed1994

Curcumin inhibits TPA induced expression of c-fos, c-jun and c-myc proto-oncogenes messenger RNAs in mouse skin.

Curcumin is a major chemical constituent of turmeric normally eaten by humans. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) is a strong promoter of chemically induced skin cancer. The exact mechanism by which TPA promotes skin cancer is not clear. However, it is known that TPA elevates the expression of oncogenes involved in cell proliferation. Recently, it has been shown that turmeric or curcumin significantly inhibits TPA-induced tumor promotion on mouse skin. However, the mechanism by which curcumin inhibits TPA-induced tumor promotion is not known. In the present studies, we investigated the effect of curcumin on the expression of c-fos, c-jun and c-myc oncogenes in TPA-treated mouse skin in CD-1 mice. A 30-nmol dose of TPA increased the levels of mRNAs for c-fos, c-jun and c-myc oncogenes by 2-3-fold compared with control. Topical application on the dorsal side of the skin with 1 mumol, 10 mumol, 20 mumol or 30 mumol of curcumin 30 min before TPA treatment inhibited the TPA-induced expression of these proto-oncogenes. Inhibition of expression of c-fos and c-jun was more pronounced than that of c-myc. A dose of 10 mumol of curcumin was found to inhibit 90% TPA-induced expression of c-fos and c-jun, and 60% of c-myc. These data strongly suggest that curcumin may inhibit skin cancer through the modulation of expression of these proto-oncogenes.

Animals↗
PubMed1994

Sex hormone-induced nuclear DNA damage and lipid peroxidation in the dorsolateral prostates of Noble rats.

To date, few studies have been reported on any aspect of DNA damage in organs of intact animals. We and others demonstrated induction of high incidences of dysplasia, a precancerous proliferative lesion, and adenocarcinoma selectively in the dorsolateral prostates (DLPs) of Noble rats exposed to a long-term combined testosterone and estradiol-17 beta treatment (T + E2-treatment). We here report induction of a significant increase in DNA strand breakage and accumulation of lipid peroxidation fluorescent products in the DLPs, but not in the ventral prostates (VPs), of rats treated with T + E2 for 16 weeks. These results indicate that this dual hormone treatment has free radical-based DNA damaging effect on rat DLP and therefore may have tumor-initiating action. Since a similar effect was not observed in regenerating DLPs of castrated rats following testosterone replacement, we conclude that the genotoxic effect of the dual hormone treatment is a direct result of hormone action and not secondarily due to enhancement of cell proliferation.

Animals↗
PubMed1994

Intracellular pH and the control of multidrug resistance.

Many anticancer drugs are classified as either weak bases or molecules whose binding to cellular structures is pH dependent. Accumulation of these drugs within tumor cells should be affected by transmembrane pH gradients. Indeed, development of multidrug resistance (MDR) in tumor cells has been correlated with an alkaline shift of cytosolic pH. To examine the role of pH in drug partitioning, the distribution of two drugs, doxorubicin and daunomycin, was monitored in fibroblasts and myeloma cells. In both cell types the drugs rapidly accumulated within the cells. The highest concentrations were measured in the most acidic compartments--e.g., lysosomes. Modifying the cellular pH in drug-sensitive cells to mimic reported shifts in MDR caused an immediate change in the cellular drug concentration. Drug accumulation was enhanced by acidic shifts and reversed by alkaline shifts. All of these effects were rapid and reversible. These results demonstrate that the alkaline shift observed in MDR is sufficient to prevent the accumulation of chemotherapeutic drugs independent of active drug efflux.

3T3 Cells↗
PubMed1994

Catheter ablation using radiofrequency or low-energy direct current in pediatric patients with the Wolff-Parkinson-White syndrome.

Percutaneous ablation of accessory pathways was performed in 22 consecutive children and adolescents (9 boys and 13 girls, age range 8 to 18 years). Low-energy direct current (DC) was used exclusively in the first 6 patients, whereas ablation was performed with radiofrequency energy in the following 16. Accessory pathways were located in the left free wall in 15 patients, were posteroseptal in 3, were in the right free wall in 3 and were anteroseptal in 1. A concealed accessory pathway was present in 7 patients (32%). There was no significant difference in clinical or electrophysiologic variables between both groups. Catheter ablation was successful in the initial 6 patients using low-energy DC, as compared with 13 of 16 patients using radiofrequency ablation. Low-energy DC was successful as a backup power source in all 3 patients who had unsuccessful radiofrequency ablation. There was no complication. The median procedural and fluoroscopic times for successful ablation were 2.5 hours and 49 minutes, respectively (p = NS between both power sources). Accessory pathway conduction recurred in 2 patients (33%) who had low-energy DC as compared with 1 (6%) who had radiofrequency ablation (p = NS). These 3 patients had successful reablation of their accessory pathways. In children and adolescents with accessory pathways, both new power sources compare favorably, with an overall success rate of ablation of 100% (22 of 22 patients). Radiofrequency ablation should be used initially because it does not require general anesthesia and is associated with a lower rate of recurrence of accessory pathway conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Catalysis of the oxidation and reduction reactions of steroid and stilbene estrogens by nuclear enzymes.

We demonstrated for the first time that nuclei were able to convert a stilbene estrogen (diethylstilbestrol) to reactive metabolites, which covalently bind to nuclear proteins and DNA. Depending on the cofactor used, nuclear enzymes catalyzed oxidation and/or reduction of stilbene and steroid estrogens. 2-Hydroxyestradiol (a major metabolite of steroidal estrogen, 17 beta-estradiol) and diethylstilbestrol (DES) were oxidized to 2,3-estradiol quinone and DES quinone, respectively, by peroxide-supported nuclear cytochromes P450. A Lineweaver-Burk plot of rate of formation of DES quinone at various substrate concentrations yielded a Km = 15 microM and Vmax = 10 nmol/mg protein/min. The oxidation of DES to DES quinone by nuclei was drastically decreased by known inhibitors of cytochromes P450. DES quinone was reduced back to DES by nuclei in the presence of NADPH, presumably through cytochrome P450 reductase. The reduction of DES quinone to DES by nuclei was significantly inhibited by antibodies and inhibitors of cytochrome P450 reductase. Under reaction conditions similar to oxidation of DES to DES quinone by nuclei, it was observed that nuclear metabolic products of DES were able to covalently bind to nuclear proteins and DNA. The data reported here establish that DES and a catechol estrogen can be oxidized to quinones and that the quinones may be reduced back to the hydroquinones by nuclear preparations when fortified with an appropriate cofactor and that reactive intermediates are involved based on observed covalent binding to macromolecules. The significance of these events, and their possible role in toxicity/cancer/teratogenicity, however, is not at all clear.

Animals↗
PubMed1994

Characterization of dairy-related Bifidobacterium spp. based on their beta-galactosidase electrophoretic patterns.

Numerical analysis of phenotypic characteristics based on enzymatic activity and carbohydrate fermentation allowed the discrimination of most strains of bifidobacteria of animal origin from those of human origin. Strains of bifidobacteria studied were separated into nine groups based on numerical analysis. Three groups contained most strains of animal origin, three groups comprised both strains of animal and human origin, and three groups were strictly composed of strains of human origin. The results indicate that one group of animal origin (group II) contained all reference strains of Bifidobacterium animals and 10 strains isolated from fermented milks or commercial preparations. Although numerical analysis of enzymatic activities and carbohydrate fermentation patterns allowed the differentiation of 'wild' strains of B. animalis and B. longum isolated from commercial preparations, this method failed to confirm the species. In the present study, the determination of electrophoretic patterns of beta-galactosidases resulted in the development of a new technique for the differentiation of Bifidobacterium species. Several isoenzymes of beta-galactosidase were detected among strains of bifidobacteria. Each species had a specific electrophoretic pattern. The detection of beta-galactosidase by electrophoresis is a new tool for distinguishing between dairy- and non-dairy-related bifidobacteria. Dairy-related bifidobacteria (B. bifidum, B. breve, B. infantis and B. longum) as well as B. animalis could be better differentiated from other bifidobacteria by comparison of their beta-galactosidase electrophoretic patterns, rather than by numerical analysis of their phenotypic characteristics.

Animals↗
PubMed1994

Preparation and characterization of novel poly(methylidene malonate 2.1.2.)-made nanoparticles.

Poly(methylidene malonate 2.1.2.) (PMM 2.1.2.) nanoparticles were prepared in phosphate buffer through emulsion polymerization of monomeric units; the kinetics of the reaction was monitored by spectrophotometry at 400 nm. Average nanoparticle sizes, molecular weights, and biodegradability of this potential drug carrier were determined under various conditions. As previously demonstrated for other similar monomers, i.e. IHCA or IBCA, pH influenced the physico-chemical characteristics of the nanoparticles obtained. Ethanol release from the ester-bearing side chains indicated that the polymers were susceptible to hydrolysis when incubated in basic pH or in rat plasma. A secondary degradation pathway, yielding formaldehyde through a reverse Knoevenagel's reaction, was minimal. Cytotoxicity studies of this new vector, in vitro, against L929 fibroblast cells demonstrated that PMM 2.1.2. nanoparticles were better tolerated than other poly(alkylcyanoacrylate) (PACA) carriers. Pharmacokinetic studies were also carried out to observe the fate of 14C-labelled PMM 2.1.2. nanoparticles after intravenous administration to rats. Forty eight hour post-injection, more than 80% of the radioactivity was recovered in urine and faeces. The body distribution of the polymer was estimated by measuring the radioactivity associated with liver, spleen, lung and kidneys. Five minutes after injection, a maximum of 24 +/- 2% of the total radioactivity was detected in the liver and less than 0.4% in the spleen. The liver-associated radioactivity decreased according to a biphasic profile and less than 8% of the total radioactivity remained after 6 days.

Animals↗
PubMed1994

Psychrotrophs in dairy products: their effects and their control.

Health concerns and technological effects of psychrotrophic bacteria in dairy products are reviewed, as well as methods to control their presence and development. The various Gram-negative and Gram-positive psychrotrophic species are listed and, with respect to pathogenic psychrotrophs, emphasis is given on Listeria monocytogenes, Yersinia enterocolitica, and Bacillus cereus. The influence of psychrotrophic bacteria on the quality of raw milk, pasteurized and UHT milks, butter, ice cream, cheese, and powders is examined. Public health considerations of Listeria monocytogenes, Yersinia enterocolitica, and Bacillus cereus of these various dairy products are also presented. Methods that can be used to eliminate or control the development of psychrotropic bacteria include low or high temperatures, chemicals, gases, the lactoperoxidase system, lactic acid bacteria, microfiltration, bactofugation, lactoferrin-related proteins, sanitation, flavors, and naturally occurring spore germinants.

Animals↗
PubMed1994

P element-mediated in vivo deletion analysis of white-apricot: deletions between direct repeats are strongly favored.

We have isolated and characterized deletions arising within a P transposon, P[hswa], in the presence of P transposase. P[hswa] carries white-apricot (wa) sequences, including a complete copia element, under the control of an hsp70 promoter, and resembles the original wa allele in eye color phenotype. In the presence of P transposase, P[hswa] shows a high overall rate (approximately 3%) of germline mutations that result in increased eye pigmentation. Of 234 derivatives of P[hswa] with greatly increased eye pigmentation, at least 205 carried deletions within copia. Of these, 201 were precise deletions between the directly repeated 276-nucleotide copia long terminal repeats (LTRs), and four were unique deletions. High rates of transposase-induced precise deletion were observed within another P transposon carrying unrelated 599 nucleotide repeats (yeast 2 mu FLP; recombinase target sites) separated by 5.7 kb. Our observation that P element-mediated deletion formation occurs preferentially between direct repeats suggests general methods for controlling deletion formation.

Alleles↗
PubMed1994

Suppressor U1 snRNAs in Drosophila.

Although the role of U1 small nuclear RNAs (snRNAs) in 5' splice site recognition is well established, suppressor U1 snRNAs active in intact multicellular animals have been lacking. Here we describe suppression of a 5' splice site mutation in the Drosophila melanogaster white gene (wDR18) by compensatory changes in U1 snRNA. Mutation of positions -1 and +6 of the 5' splice site of the second intron (ACG[GTGAGT to ACC]GTGAGC) results in the accumulation of RNA retaining this 74-nucleotide intron in both transfected cells and transgenic flies. U1-3G, a suppressor U1 snRNA which restores base-pairing at position +6 of the mutant intron, increases the ratio of spliced to unspliced wDR18 RNA up to fivefold in transfected Schneider cells and increases eye pigmentation in wDR18 flies. U1-9G, which targets position -1, suppresses wDR18 in transfected cells less well. U1-3G,9G has the same effect as U1-3G although it accumulates to lower levels. Suppression of wDR18 has revealed that the U1b embryonic variant (G134 to U) is active in Schneider cells and pupal eye discs. However, the combination of 9G with 134U leads to reduced accumulation of both U1b-9G and U1b-3G,9G, possibly because nucleotides 9 and 134 both participate in a potential long-range intramolecular base-pairing interaction. High levels of functional U1-3G suppressor reduce both viability and fertility in transformed flies. These results show that, despite the difficulties inherent in stably altering splice site selection in multicellular organisms, it is possible to obtain suppressor U1 snRNAs in flies.

Alternative Splicing↗
PubMed1994

TGF-beta 1 gene expression in cultured human keratinocytes does not decrease with biologic age.

The biologic activity of cultured epithelial grafts is believed to diminish with increasing cellular age. Therefore, keratinocytes from young donors are used preferentially in the production of cultured allografts for wound treatment. However, the impact of biologic age on cytokine gene expression by human keratinocytes has not been previously investigated. In this study, transforming growth factor-beta 1 (TGF-beta 1) gene expression in human keratinocytes derived from normal foreskins of males ranging in age from 7 months to 82 years was analyzed. Keratinocytes were harvested from fresh specimens and cultivated in vitro on 3T3 fibroblast feeder layers through second passage. The cells were analyzed both qualitatively and semiquantitatively for TGF-beta 1 gene expression using three separate techniques: in situ hybridization, Northern hybridization, and competitive polymerase chain reaction. By in situ hybridization, the signal representing TGF-beta 1 transcript was detected in cells in all layers of the stratified cultures, and immunohistochemical staining for TGF-beta 1 protein was equally intense in all layers. Northern blots of total RNA extracted from the cultivated cells showed no decrease in band density with increasing biologic age. Likewise, no decrease in TGF-beta 1 mRNA levels with biologic age was observed using a semiquantitative polymerase chain reaction assay. These results indicate that the potential for TGF-beta 1 gene expression in cultured foreskin keratinocytes does not decline with increasing cellular age. The findings imply that the clinical performance of cultured grafts, at least as it relates to the elaboration of this growth factor, may not be significantly altered by the biologic age of the keratinocyte donor.

Adult↗
PubMed1994

Diminished diabetogenic effect of streptozotocin in adrenodemedullated rats.

Although stress is suspected to play a role in the development of diabetes mellitus, no direct experimental evidence for involvement of the adrenal medullae in onset of the disease has yet been found. We recently observed that, in comparison with sham-operated rats, fewer adrenodemedullated rats become diabetic after an i.v. injection of streptozotocin (STZ); thus, the present study examined the role of the adrenal medullae in the development of experimental diabetes. Male Wistar rats were surgically adrenodemedullated (ADM) or sham-operated (SHAM). After a 3-week recovery period, they were injected with 40 mg STZ/kg freshly dissolved in citrate buffer or buffer alone. A 1-mL arterial blood sample was withdrawn 12 days later in previously cannulated animals; then the rats were killed and their pancreas was removed. The plasma glucose levels were lower in ADM rats injected with buffer alone than in their SHAM counterparts (7.7 +/- 0.1 vs. 8.5 +/- 0.1 mmol/L; p < 0.05). The glucose levels were higher (p < 0.001) in both groups of STZ-treated rats, with values 28% lower in ADM than in SHAM rats (14.7 +/- 1.6 vs. 18.8 +/- 1.2 mmol/L; p < 0.03). Whereas plasma insulin levels did not differ between ADM and SHAM rats injected with buffer alone (431 +/- 38 vs. 428 +/- 35 pmol/L; p > 0.05), they were diminished in SHAM animals injected with STZ (292 +/- 37 vs. 428 +/- 35 pmol/L; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1994

Heparin-binding epidermal growth factor-like growth factor is differentially regulated by progesterone and estradiol in rat uterine epithelial and stromal cells.

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) cDNA was isolated from a subtracted cDNA library that selected for progesterone-induced transcripts from rat uterine stromal cells. In this study, the effects of progesterone and estradiol on the expression of HB-EGF in mature rat uterine epithelial and stromal cells have been examined. RNase protection assays and in situ hybridization demonstrated that progesterone stimulated expression of HB-EGF in rat uterine stromal cells, but repressed levels of HB-EGF mRNA in luminal and glandular epithelial cells. In contrast, estradiol treatment strongly enhanced HB-EGF expression in epithelial cells, but had no effect on mRNA levels for this growth factor in stromal cells. Progesterone treatment followed by estradiol injection stimulated HB-EGF expression in stromal cells and repressed expression in luminal and glandular epithelium. Stimulation of HB-EGF expression in stromal cells by progesterone was not inhibited by treatment with cycloheximide, demonstrating that HB-EGF mRNA expression is a primary response of stromal cells to progesterone. These results reveal that expression of HB-EGF is stimulated in epithelial and stromal cells in vivo under the same hormonal conditions that induce cell proliferation in each of these cell types and strongly suggest that HB-EGF may mediate the mitogenic effects of steroid hormones in the rat uterus.

Animals↗
PubMed1994

Radiation doses to patients in neurointerventional procedures.

PURPOSE: To evaluate stochastic and deterministic risks associated with neurointerventional procedures for the patient. METHODS: Eight neurovascular interventional procedures were evaluated to determine the entrance skin dose and effective dose for the patient. Dosimetry was done with thermoluminescence dosimeters. The highest dose on the patient's head was recorded as the maximum entrance skin dose. The equivalent dose was obtained by conversion of the dose-area product using published conversion tables. RESULTS: The maximum entrance skin dose varied from 129 to 1335 mGy. The mean effective dose was 1.67 mSv with a range of 0.44 to 3.44 mSv. No deterministic effect has been encountered. Stochastic risk linked to the highest effective dose value was approximately one death by fatal cancer for every 6000 procedures, according to the new International Commission on Radiological Protection coefficient. CONCLUSIONS: Because no deterministic effect has been detected, and stochastic risks were very low, radiation hazard to the patient is a minor consideration in deciding whether to undertake a neurointerventional procedure.

Adult↗