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Biomedical subjects

R Davies

Publications and source records attributed to R Davies.

At least 19 recordsLinked to original sources
PubMed1997

Noninvasive, real-time method for the examination of thymidine uptake events--application of the method to V-79 cell synchrony studies.

[14C]Thymidine uptake into V-79 hamster lung fibroblasts has been successfully demonstrated using a noninvasive, real-time method utilizing Cytostar-T scintillating microplates. These plates are standard format, tissue culture-treated, 96-well microplates with an integral scintillating base. The microplates permit the culture and observation of adherent cell monolayers. Biological activities of the cells can be studied by the provision of specific radiolabeled compounds. The biological activities of the adherent monolayer bring the specific radiolabel into proximity with the scintillating base and a scintillation signal is thereby generated. [14C]Thymidine incorporation on the microplates can be used to examine cell proliferation and cell cycle events. Using a combined mitotic shake-off/aphidicolin treatment to achieve synchronization, the thymidine incorporation activities of V-79 cells have been examined on Cytostar-T plates and correlated to traditional methods of determining incorporation. The method was further used to examine the effects of colcemid and olomoucine, both chemical inhibitors of cell proliferation, on synchronous populations of cells. The homogeneous detection format and the microplate nature of the method suggest a role for scintillating microplates in cell biology research and drug discovery.

Animals↗
PubMed1997

Tamoxifen causes gene mutations in the livers of lambda/lacI transgenic rats.

Tamoxifen, a rat liver carcinogen, was administered to female lambda/lacI transgenic rats at a dose of 20 mg/kg body weight by gavage for 6 weeks, and the animals were sacrificed 2 weeks later. Tamoxifen induced liver DNA adducts and caused a significant increase in mutation frequency (MF) of approximately 3-fold at the lacI gene in liver DNA. Liver DNA from animals dosed with tamoxifen at 10 mg/kg also showed a similar increase in MF. The mutations were characterized by a raised proportion of: (a) G:C to T:A transversions; (b) insertions of base pairs; and (c) deletions of pairs of G:C base pairs. These observations indicate that tamoxifen induces a distinct spectrum of mutations compared with that found in controls. Toremifene, a noncarcinogenic analogue of tamoxifen with similar estrogenic/antiestrogenic properties examined at 20 mg/kg body weight using the same dosing regime as tamoxifen was not mutagenic. A single oral dose of the rat liver carcinogen aflatoxin B1 (0.5 mg/kg) also significantly raised the MF. In conclusion, although tamoxifen is not mutagenic in regulatory short-term tests, it is a gene mutagen in the rat liver.

Aflatoxins↗
PubMed1997

Oral delivery of foreign antigens by attenuated Salmonella: consequences of prior exposure to the vector strain.

Several strains of Salmonella have been used as vectors for the delivery of Escherichia coli fimbrial proteins to the gut-associated lymphoid tissue (GALT) of the mouse. Plasmids carrying a complementing thyA+ gene, together with genes specifying synthesis of K88 or K99, were introduced into non-reverting thyA Salmonella mutants. The resulting constructs expressed the foreign pilin protein on their surfaces and, provided the vector was able to colonize the GALT, elicited strong serum responses to K88 or K99. These responses were dramatically impaired however, in recipients with pre-existing immunity to the vector strain. Mice initially infected with Salmonella stanley ca 4, 10 or 20 weeks prior to oral administration of S. stanley-K88 showed greatly reduced serum responses to K88 as determined by ELISA. The hypo-responsiveness seen in vector-primed mice could be largely overcome by changing the serotype of the strain subsequently used to deliver the foreign protein.

Administration, Oral↗
PubMed1997

Electropotential evaluation as a new technique for diagnosing breast lesions.

A new approach, termed the Biofield test, may have the potential to augment the process of diagnosing breast cancer. This technique is based on the analysis of skin surface electrical potentials measured by an array of specially designed sensors which are placed on the breasts. Measurements are recorded noninvasively and then analyzed using pattern recognition algorithms to produce an immediate and objective assessment of breast tissue in vivo. Initial clinical trials suggests that the test can achieve a sensitivity of approximately 90% and a specificity of 40-50%, which indicates that the test might be useful for excluding cancer when it is, in fact, absent. Although research to date has focused on the differential diagnosis of suspicious breast lesions, future applications could include breast cancer screening, close surveillance and diagnosis of recurrent cancers in breasts previously treated with conservative therapy, and monitoring the effectiveness of breast cancer therapies. Improvements and new applications are expected to occur as additional research and validation in actual clinical settings is performed.

Algorithms↗
PubMed1997

A detailed angiographic analysis of patients with ambulatory electrocardiographic ischemia: results from the Asymptomatic Cardiac Ischemia Pilot (ACIP) study angiographic core laboratory.

OBJECTIVES: The purpose of this Asymptomatic Cardiac Ischemia Pilot (ACIP) data bank study was to characterize angiographic features of coronary pathology of patients enrolled in the ACIP study. BACKGROUND: Ischemia during ambulatory electrocardiographic (AECG) monitoring is associated with increased morbidity and mortality. Reports relating AECG ischemia to severity or complexity of coronary artery disease are few in number and small in size and have produced conflicting results. METHODS: Coronary angiograms from patients with asymptomatic AECG ischemia enrolled in the ACIP study were reviewed at a central core laboratory. Quantitative measurement of percent stenosis and Thrombolysis in Myocardial Infarction flow grades were used to assess the severity of coronary artery disease. Lesions were also evaluated for the presence of intracoronary thrombus, ulceration and lumen contour as indicators of stenosis complexity. In addition, comparisons were made with 27 patients screened for the ACIP study, but who were found ineligible because they did not have AECG ischemia on 48-h Holter monitoring. RESULTS: A total of 329 (75%) of 439 patients with AECG ischemia had multivessel coronary artery disease. Proximal stenoses > or = 50% diameter reduction were common in patients with AECG ischemia (62.2%), as were proximal stenoses > or = 70% (38.7%). Features suggesting complex plaque were found in 50.1% of patients with AECG ischemia. CONCLUSIONS: Multivessel coronary artery disease, severe proximal stenoses and features of complex plaque were observed frequently in patients who exhibited AECG ischemia. The presence of severe and complex coronary artery disease may explain, in part, the increased risk for adverse outcome associated with ischemia during activities of daily life.

Coronary Angiography↗
PubMed1997

Clastogenic and aneugenic effects of tamoxifen and some of its analogues in hepatocytes from dosed rats and in human lymphoblastoid cells transfected with human P450 cDNAs (MCL-5 cells).

Tamoxifen and its analogues 4-hydroxytamoxifen, toremifene, 4-hydroxytoremifene, clomifene and droloxifene were tested for clastogenic effects in a human lymphoblastoid cell line (MCL-5) expressing elevated native CYP1A1 and containing transfected CYP1A2, CYP2A6, CYP2E1 and CYP3A4 and epoxide hydrolase and in a cell line containing only the viral vector (Ho1). MCL-5 or Ho1 cells were incubated with 4-hydroxytamoxifen, 4-hydroxytoremifene, clomifene or droloxifene and the incidence of micronuclei estimated. With MCL-5 cells there was an increase in micronuclei with 4-hydroxytamoxifen, 4-hydroxytoremifene and clomifene but not with droloxifene. With Ho1 cells only 4-hydroxytamoxifen and 4-hydroxytoremifene caused an increase in micronuclei. MCL-5 cells were incubated with tamoxifen, 4-hydroxytamoxifen, toremifene, droloxifene, clomifene or diethylstilbestrol (0.25-10 microg/ml) for 48 h and subjected to 3 h treatment with vinblastine (0.25 microg/ml) to arrest cells in metaphase. The incidence of cells with chromosomal numerical aberrations (aneuploidy) was increased in cells treated with tamoxifen, 4-hydroxytamoxifen, toremifene, clomifene and diethylstilbestrol but not droloxifene. The frequency of cells with structural abnormalities (excluding gaps) was increased in cells treated with tamoxifen and toremifene but not 4-hydroxytamoxifen, clomifene, droloxifene or diethylstilbestrol. The clastogenic activities of tamoxifen (35 mg/kg), toremifene (36.3 mg/kg), droloxifene (35.2 mg/kg) and diethylstilbestrol (25 mg/kg) were compared in groups of four female Wistar rats. Each chemical was dissolved in glycerol formal, administered as a single dose by gavage and hepatocytes isolated by collagenase perfusion 24 h later. The cells were cultured in the presence of epidermal growth factor (40 ng/ml) for 48 h, colchicine (10 microg/ml) being added for the final 3 h of incubation. At least 100 chromosomal spreads were examined from each animal for the presence of numerical and structural abnormalities. The incidences of aneuploidy following treatment were: tamoxifen 81%, toremifene 46%, droloxifene 9.6%, diethylstilbestrol 45.7%, vehicle control 5.3%. The incidences of chromosomal structural abnormalities excluding gaps were: tamoxifen 4.3%, toremifene 0.8%, droloxifene 0.5%, diethylstilbestrol 0.8%, control 0.5%. The incidence of chromosomal structural aberrations excluding gaps in the treated animals was not statistically significantly different from controls except in the tamoxifen-treated group. Tamoxifen (35 mg/kg per os) and toremifene (36.3 mg/kg per os) were dosed to rats for 4 weeks and chromosomal spreads made from hepatocytes. The incidences of aneuploidy were: tamoxifen 94%, toremifene 57%, control 6.5%. The incidences of chromosomal aberrations excluding gaps were: tamoxifen 12%, toremifene 1%, control 0.5%. The incidence of tamoxifen-induced chromosomal structural abnormalities was significantly elevated compared with control levels. The results demonstrate that tamoxifen and toremifene are the only two drugs tested in the study that cause chromosomal structural and numerical aberrations in vitro and tamoxifen is the only drug that induces both these effects in rat liver cells stimulated to divide in culture following oral dosing. Since chromosomal mutations require cell division for their manifestation and tamoxifen is the only compound of those tested that causes hyperplasia in the rat liver, chromosomal aberrations and aneuploidy in the rat liver would only be expected to occur following treatment with tamoxifen alone, although aneuploidy could be induced by toremifene in conjunction with a promoter such as phenobarbitone.

Aneuploidy↗
PubMed1997

Prevalence of suspected periodontal pathogens identified using ELISA in adolescents of differing ethnic origins.

The aim of this study was to determine the prevalence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia in a group of adolescents and investigate the association of these organisms with various clinical parameters. A total of 527, 11-13-year-old children, of whom 333 (63%) were white Caucasian, 187 (35%) Indo-Pakistani and 7 (1%) Afro-Caribbean, participated in the study. Subgingival plaque samples, collected from the mesio-buccal of both upper first permanent molars using sterile paper points, were stored in phosphate buffered saline with 0.01% thiomersal and analysed for the presence of A. actinomycetemcomitans, P. gingivalis and P. intermedia using ELISA. The mesio-buccal sites of both upper 1st permanent molars were also examined and the presence/absence of supragingival plaque, subgingival calculus, bleeding on probing and pocket depths greater than 3 mm were recorded. The % of white Caucasian children in whom the monoclonal antibody identified at least 1 site with A. actinomycetemcomitans, P. gingivalis and P. intermedia were 4%, 3% and 2%, respectively, and for Indo-Pakistanis were 3%, 17% and 2%. The difference for P. gingivalis was statistically significant (p < 0.001). The associations between the clinical parameters and the 3 organisms were considered separately for both upper first molar sites. The prevalence of P. gingivalis was higher for sites with subgingival calculus, pockets > 3 mm and bleeding on probing (p < 0.01).

Adolescent↗
PubMed1997

The value of including broth cultures as part of a routine culture protocol.

Three hundred seventeen clinical specimens from both superficially and deeply infected sites were prospectively examined to assess the true value of including liquid media as part of the routine culture procedure. All broth cultures were subcultured after overnight incubation onto plate media. The isolates obtained from the broth cultures were then compared with the isolates obtained on primary solid media. The isolates obtained from the broth cultures only were evaluated for clinical relevance by review of the patients' records. Twenty-two clinically relevant isolates were obtained from the broth cultures only, but the isolation of these additional organisms altered patient management for only two patients. It would appear from these results that the additional expense and time involved in culturing clinical specimens in fluid media is unwarranted.

Bacterial Typing Techniques↗
PubMed1996

Mutational spectra of tamoxifen-induced mutations in the livers of lacI transgenic rats.

Tamoxifen, an important drug in breast cancer treatment, causes liver cancer in rats. The standard range of in vitro tests have failed to show that it causes DNA damage, but 32P-postlabelling and DNA-binding studies have shown that tamoxifen forms DNA adducts in rat liver. In 1995 a transgenic rat (Big Blue; Stratagene, La Jolla, CA) became available which harbours the bacterial lacI gene, thereby allowing the in vivo study of tamoxifen mutagenesis. Recently, we [Styles JA et al. (1996): Toxicologist 30; 161] showed that tamoxifen caused on increase in the mutation frequency at the lacI gene in these transgenic rats. In this study, we report on our preliminary analysis of the mutational spectra of 33 control and 38 tamoxifen-induced mutant lacI genes. Plasmid DNA containing the lacI gene was isolated from the mutant phages and its DNA sequence determined. In the control animal group, 81% of the mutant lacI genes were point mutations, whilst in the tamoxifen-treated group, 62% of the mutant lacI genes were point mutations. Of the tamoxifen-induced mutants, 43% were GC-->TA transversions and 70% of point mutations. In the control group, GC-->TA transversions were 19% of all mutations and 24% of point mutations. Thus, compared with control animals, tamoxifen treatment had significantly increased the proportion of GC-->TA transversions.

Animals↗
PubMed1996

Prostate epithelial differentiation is dictated by its surrounding stroma.

Prostate epithelial differentiation is dictated by its surrounding stroma which determines androgen induced growth responsiveness and expression of specific secretory proteins in normal prostate gland. During neoplastic progression, organ specific stroma has been shown to determine the rate of neoplastic progression from androgen-dependent to androgen-independent and metastatic states. Although growth factors and extracellular matrix are recognized as important contributors to prostate epithelial growth, hormonal responsiveness, and neoplastic progression, the exact mechanism of intercellular communication between stromal and epithelial cells remains undefined. In addition to the importance of defining the reciprocal interaction between stromal and epithelial interaction in the prostate, clonal interaction between two dissimilar prostate epithelial cell is also recognized to contribute to disease progression. In this review, we summarized recent advances made in delineating molecular mechanisms underlying stromal epithelial interaction and clonal interaction between androgen-dependent and androgen-independent prostate cancer cells in vivo and in culture. Understanding cellular interaction between prostate epithelium and its surrounding stroma could help us in developing metastatic models of prostate carcinogenesis. This concept will allow us to define epithelial-specific markers, markers induced as the result of stromal-epithelial interaction, and stroma-associated markers. These markers together will assist us in diagnosing, preventing, prognosing and treating prostate cancer more efficaciously in the future.

Androgens↗
PubMed1996

Comparison of staurosporine and four analogues: their effects on growth, rhodamine 123 retention and binding to P-glycoprotein in multidrug-resistant MCF-7/Adr cells.

The potent kinase inhibitor staurosporine and its protein kinase C (PKC)-selective analogue CGP 41251 are known to sensitise cells with the multidrug resistance (MDR) phenotype mediated by P-glycoprotein (P-gp) to cytotoxic agents. Here four PKC-selective staurosporine cogeners, CGP 41251, UCN-01, RO 31 8220 and GF 109203X, were compared with staurosporine in terms of their MDR-reversing properties and their susceptibility towards P-gp-mediated drug efflux from MCF-7/Adr cells. Staurosporine was the most potent and the bisindolylmaleimides RO 31 8220 and GF 109203X the least potent cytostatic agents. When compared with MCF-7 wild-type cells, MCF-7/Adr cells were resistant towards the growth-arresting properties of RO 31 8220 and UCN-01, with resistance ratios of 12.6 and 7.0 respectively. This resistance could be substantially reduced by inclusion of the P-gp inhibitor reserpine. The ratios for GF 109203X, staurosporine and CGP 41251 were 1.2, 2.0 and 2.9 respectively, and they were hardly affected by reserpine. These results suggest that RO 31 8220 and UCN-01 are avidly transported by P-gp but that the other compounds are not. Staurosporine and CGP 41251 at 10 and 20 nM, respectively, decreased efflux of the P-gp probe rhodamine 123 (R123) from MCF-7/Adr cells, whereas RO 31 8220 and GF 109203X at 640 nM were inactive. CGP 41251 was the most effective and GF 109203X the least effective inhibitor of equilibrium binding of [3H]vinblastine to its specific binding sites, probably P-gp, in MCF-7/Adr cells. Overall, the results imply that for this class of compound the structural properties that determine susceptibility towards P-gp-mediated substrate transport are complex. Comparison with ability to inhibit PKC suggests that the kinase inhibitors affect P-gp directly and not via inhibition of PKC. Among these compounds CGP 41251 was a very potent MDR-reversing agent with high affinity for P-gp and least affected by P-gp-mediated resistance, rendering it an attractive drug candidate for clinical development.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Regulation of P-glycoprotein 1 and 2 gene expression and protein activity in two MCF-7/Dox cell line subclones.

The MCF-7 doxorubicin-resistant cell line MCF-7/Dox has been used extensively for studies of the multidrug resistance phenomenon. Using fluorescence-activated cell sorting (FACS), these cells were separated into two populations on the basis of rhodamine 123 (R123) accumulation. We designated these as low P-glycoprotein (LP-gp) and high P-gp (HP-gp) cells on the basis of their P-gp content. Using the reverse transcriptase polymerase chain reaction technique controlled by homologous internal standards, we analysed levels of MDR1 and MDR2 mRNA in each cell type. LP-gp and HP-gp cells had MDR1 mRNA levels of 2.17 +/- 0.17 and 6.65 +/- 2.29 amol ng-1 total RNA respectively, compared with 0.00088 +/- 0.00005 amol ng-1 in wild-type MCF-7 cells (MCF-7/WT). MCF-7/WT cells additionally contained 0.023 +/- 0.016 amol ng-1 of MDR2 mRNA, which was unchanged in LP-gp cells, but lower than in HP-gp cells, which contained 0.42 +/- 0.08 amol ng-1. Both LP-gp and HP-gp cells contained increased copies of the MDR1 gene. However, the degree of gene amplification did not correlate with the changes in MDR1 mRNA levels, indicating further regulatory levels of gene expression. The level of P-gp detected by MRK 16 correlated with R123 accumulation. HP-gp cells expressed a 10-fold higher level of P-gp1 than LP-gp cells. However, there was only a 3-fold increase in MDR1 mRNA level in HP-gp cells compared with LP-gp cells. These data suggest that some regulation of P-gp1 expression also occurred at the post-translational level. Phosphorylation of P-gp by protein kinase C (PKC)-alpha is necessary for its activity. Our analysis of PKC-alpha, 0 and epsilon isozyme levels, and subcellular distribution, shows a co-regulation of expression with P-gp, suggesting a necessary role for PKC in P-gp regulation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Simulation of diabetic eye disease to compare screening policies.

AIMS/BACKGROUND: The purpose of the project was to develop a technique for evaluating screening policies in the treatment of insulin dependent diabetic retinopathy. The study was concerned with patients who contracted the disease, aged under 35 years. Simulation was used to describe the progress of a cohort of patients through disease and treatment. METHOD: Data, derived from a literature survey of European and American population and clinic studies, were used to model as closely as possible the development of retinopathy in all its stages, together with the effects of screening and treatment. The model output was validated against published data. RESULTS: The results showed that where screening sensitivities are high, the frequency of screening makes little difference to the years of sight saved, but it does make a difference if screening sensitivities are close to 50%. CONCLUSIONS: Although annual screening is normally desirable, biannual screening could be considered where patient compliance and screening sensitivities are both high.

Adolescent↗
PubMed1996

Asian women are at increased risk of gestational thyrotoxicosis.

Gestational thyrotoxicosis is now widely believed to result from excessive thyroidal stimulation by hCG. Our clinical impression has been that this condition is more frequent in Asian women than in those of European origin. To assess this possibility further, we analyzed thyroid hormone levels in the sera of 294 Asian women, obtained as part of a screening program at 15-16 weeks of pregnancy, and compared these with 292 sera from age- and parity-matched European women at a similar time of gestation. TSH levels were significantly lower in the Asian group (P < 0.001). Suppressed TSH levels (< 0.35 mIU/L) were found in 15.7% of Asian women and 4.8% of European women (P < 0.001). In both groups of women with suppressed TSH values, hCG and hCG beta levels were higher than in the women with normal TSH levels. Free T4 levels in the Asian women were significantly higher in those with suppressed TSH (P < 0.001), but this was not found in the European women. There was also a significant increase in the free T3 index in the Asian women with suppressed TSH compared to that in an age-matched group of Asian women with normal TSH levels (P < 0.02), but this was not observed in European women with suppressed TSH. None of the women with suppressed TSH had thyroid-stimulating antibodies. These results show that Asian women more frequently develop biochemical evidence of thyrotoxicosis at the beginning of the second trimester of pregnancy than those of European origin and are, therefore, likely to be at greater risk of clinically apparent gestational thyrotoxicosis and hyperemesis gravidarum. Genetically determined differences in the production or metabolism of hCG isoforms may account for this increased risk.

Asian People↗