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Biomedical subjects

A Rose

Publications and source records attributed to A Rose.

At least 37 records · Page 2Linked to original sources
PubMed2001

Quinoprotein glucose dehydrogenase modified thick-film electrodes for the amperometric detection of phenolic compounds in flow injection analysis.

The use of thick-film electrodes as basic transducers for highly sensitive amperometric biosensors using PQQ (pyrroloquinoline quinone) dependent glucose dehydrogenase (GDH) with short response times is described. The enzyme is embedded in a polyurethane matrix on top of a platinum based thick film electrode and its ability to reduce oxidized phenolic compounds is exploited. The electrochemical amplification is based on the oxidation of the analyte on the surface of the electrode followed by its enzymatic reduction. Different parameters of the glucose dehydrogenase electrode system using dopamine as a model analyte were optimized, e.g., membrane thickness, pH value, buffer system, flow rate and storage conditions. Using optimized parameters the sensitivity and detection limits for various phenolic compounds were evaluated. The comparison of electrodes from the identical as well as from different batches shows the ability to produce a number of well reproducible sensors showing remarkably small differences with respect to parameters as sensitivity, response times and measuring range.

Acinetobacter calcoaceticus↗
PubMed2001

The simultaneous determination of diazepam and its three metabolites in dog plasma by high-performance liquid chromatography with mass spectroscopy detection.

A fast, sensitive and specific LC/MS/MS method for the simultaneous determination of diazepam and its three metabolites, oxazepam, temazepam and desmethyldiazepam, in dog plasma is described. The method consists of an automated 96-well solid phase extraction procedure and electrospray LC/MS/MS analysis. D(5)-Diazepam is used as the internal standard for all the compounds. Intra-day and inter-day assay coefficients of variations are less than 12.7%. The lower limit of quantitation (LLOQ) is 1 nM for each analyte, based on 0.1 ml aliquots of dog plasma. The analytical run time was 5 min. Linearity is observed over the range of 1--500 nM. This method has been used to support the discovery of pharmacokinetic studies.

Animals↗
PubMed2001

Retention of low income mothers in a parenting intervention study.

Women with inadequate prenatal care were recruited to a multi-component parenting intervention study. Because it was anticipated that this high-risk population might present challenges to retention, a variety of strategies were employed to maintain their participation in the study. This report reviews the results of these retention efforts and compares the population that completed the study versus those that terminated prior to study completion. Two hundred and eighty-six women were randomized to an intervention or control group. Careful tracking of the mothers, offering incentives for completing various study activities and providing a culturally competent staff were among the strategies employed to maintain participation. Comparison was made of those mothers terminating before study completion versus those retained, and of those terminating early in the study period versus later. Despite retention efforts, attrition at a level of 41% occurred. A few characteristics of mothers terminating early from the study were significant including older maternal age, a larger number of children, and incidence of no prenatal care. Despite comprehensive tracking procedures, some mothers were lost to follow up after change of residence. Other reasons for attrition included child outplacement and refusal of services or data collection procedures.

Adult↗
PubMed2000

Suberoylanilide hydroxamic acid, an inhibitor of histone deacetylase, suppresses the growth of prostate cancer cells in vitro and in vivo.

Suberoylanilide hydroxamic acid (SAHA) is the prototype of a family of hybrid polar compounds that induce growth arrest in transformed cells and show promise for the treatment of cancer. SAHA induces differentiation and/or apoptosis in certain transformed cells in culture and is a potent inhibitor of histone deacetylases. In this study, we examined the effects of SAHA on the growth of human prostate cancer cells in culture and on the growth of the CWR22 human prostate xenograft in nude mice. SAHA suppressed the growth of the LNCaP, PC-3, and TSU-Pr1 cell lines at micromolar concentrations (2.5-7.5 microM). SAHA induced dose-dependent cell death in the LNCaP cells. In mice with transplanted CWR222 human prostate tumors, SAHA (25, 50, and 100 mg/kg/day) caused significant suppression of tumor growth compared with mice receiving vehicle alone; treatment with 50 mg/kg/day resulted in a 97% reduction in the mean final tumor volume compared with controls. At this dose, there was no detectable toxicity as evaluated by weight gain and necropsy examination. Increased accumulation of acetylated core histones was detected in the CWR22 tumors within 6 h of SAHA administration. SAHA induced prostate-specific antigen mRNA expression in CWR22 prostate cancer cells, resulting in higher levels of serum prostate-specific antigen than predicted from tumor volume alone. The results suggest that hydroxamic acid-based hybrid polar compounds inhibit prostate cancer cell growth and may be useful, relatively nontoxic agents for the treatment of prostate carcinoma.

Animals↗
PubMed2000

A novel mechanism of cell killing by anti-topoisomerase II bisdioxopiperazines.

Bisdioxopiperazines are a unique class of topoisomerase II inhibitors that lock topoisomerase II at a point in the enzyme reaction cycle where the enzyme forms a closed clamp around DNA. We examined cell killing by ICRF-187 and ICRF-193 in yeast cells expressing human topoisomerase II alpha (htop-IIalpha). Expression of htop-IIalpha in yeast cells sensitizes them to both ICRF-187 and ICRF-193, compared with cells expressing yeast topoisomerase II. ICRF-193 is still able to exert growth inhibition in the presence of genes encoding both ICRF-193-resistant and ICRF-193-sensitive htop-IIalpha enzymes, indicating that sensitivity to bisdioxopiperazines is dominant. Killing by ICRF-193 occurs more rapidly, than the killing in yeast cells due to a temperature-sensitive yeast topoisomerase II incubated at the non-permissive temperature. These results are reminiscent of a top-II poison such as etoposide. However, the killing caused by ICRF-193 and ICRF-187 is not enhanced by mutations in the RAD52 pathway. The levels of drug-induced DNA cleavage observed with htop-IIalpha in vitro is insufficient to explain the sensitivity induced by this enzyme in yeast cells. Finally, arrest of cells in G(1) does not protect cells from ICRF-193 lethality, a result inconsistent with killing mechanisms due to catalytic inhibition of top-II or stabilization of a cleavable complex. We suggest that the observed pattern of cell killing is most consistent with a poisoning of htop-II by ICRF-193 by a novel mechanism. The accumulation of closed clamp conformations of htop-II induced by ICRF-193 that are trapped on DNA might interfere with transcription, or other DNA metabolic processes, resulting in cell death.

Alleles↗
PubMed2000

Erythropoietic reconstitution, macrophages and reticulin fibrosis in bone marrow specimens of CML patients following allogeneic transplantation.

A clinicopathological study was conducted on 351 bone marrow trephine biopsies derived from 124 patients with chronic myeloid leukemia (CML) at standardized endpoints before and after allogeneic bone marrow transplantation (BMT). The purpose was to investigate quantitative changes of the nucleated erythroid precursor cell population and other associated features such as resident bone marrow macrophages and myelofibrosis and to elucidate their relevance on engraftment parameters. Monoclonal antibodies were applied for the identification of erythroid precursors and the labeling of mature macrophages; argyrophilic (reticulin-collagen) fibers were demonstrated by a silver impregnation technique. Following morphometric analysis of the pregraft bone marrow specimens statistical evaluation was in line with an adverse correlation between early to moderate reticulin fibrosis and amount of erythropoiesis. Moreover, a significant relationship was calculable between numbers of erythroid precursors and CD68+ macrophages. After myelo-ablative therapy and BMT a pronounced decrease in cellularity and in the quantity of erythropoiesis was found. Comparable with the pregraft samples, a significant association between erythroid precursors and macrophages could be determined in the regenerating donor bone marrow. A pretransplant relevant reduction of the red cell lineage and a manifest (reticulin) myelofibrosis indicating an advanced stage of disease were accompanied by a significant delay to reach transfusion independence. This result was further supported by comparable findings in trephine biopsies performed in the early post-transplant period (second month after BMT). Corresponding examinations revealed an enhancement of fiber density and a decrease in erythropoiesis in those patients who did not conform with the usually accepted criteria for successful engraftment. In conclusion, compelling evidence has been produced that a significantly reduced amount of erythroid precursors, which is usually associated with myelofibrosis in the pretransplant bone marrow, exerts an impairment to undisturbed hematopoietic reconstitution. Moreover, a close spatial and numerical relationship between the erythroid lineage and resident (mature) macrophages is observable, in particular in the state of regeneration after BMT.

Adolescent↗
PubMed2000

Mantle planning: report of the Australasian Radiation Oncology Lymphoma Group film survey and consensus guidelines.

The purpose of the present paper was to measure the variation in mantle planning in Australia and New Zealand. A chest X-ray (CXR) of a patient in the supine position with a neck node marked by wire was sent to every radiation oncologist in Australia and New Zealand. They were to mark on the CXR the lung blocks that they would use to treat this patient, assuming that the patient had stage IA Hodgkin's disease. These marks were compared with a small sample of radiologists who were asked to define the mediastinum on the same CXR. Radiation oncologists were also asked to complete a short questionnaire about other modifications to their treatment fields and their experience with this technique. One hundred and six films were sent out and 44 radiation oncologists replied. There was a maximum variation in the placement of their lung blocks of 6 cm. Half of the lung blocks were within a 2-cm range. One respondent said they would not use a mantle field to treat this patient. Mediastinal coverage was inadequate in at least 50% of cases. There was a very large variation in mantle field planning practices within Australia and New Zealand. For this reason Australasian Radiation Oncology Lymphoma Group has produced consensus guidelines for mantle block design. These are appended to the present paper.

Australia↗
PubMed2000

Functional instability in non-contact ankle ligament injuries.

OBJECTIVES: To measure objectively functional standing balance in the acute stages of non-contact ankle sprain, and to compare patients with controls. METHODS: A Chattanooga balance machine was used to measure postural stability in patients with acute ankle sprain and uninjured controls over a two week period, in one and two legged stance, with eyes open and closed. Participants also completed the Olerud and Molander questionnaire to provide a subjective measure of ankle function. RESULTS: There was a highly significant improvement in questionnaire scores for the patients during the study period (p<0.0001). Patients appeared to be less stable than controls in all balance tests, although the difference did not reach significance. There was evidence of improvement over time in the number of tests successfully completed on the injured leg in single legged stance with eyes closed (p = 0.043) between visits 1 and 3. CONCLUSIONS: The patient group showed a subjective improvement, which supports clinical experience of treating acute ankle injuries. There is some evidence that on average the patient group appeared to be less stable than controls in all balance tests, although the difference did not reach statistical significance, even on the uninjured leg. There is a need to carry out further studies to confirm the results found in this pilot study and to investigate the hypotheses generated. It would be useful to evaluate a simple test that could be used clinically to monitor progress after ankle injury, and also to identify athletes with decreased functional stability, who may be more at risk of sustaining ankle injury.

Adult↗
PubMed1999

Human small cell lung cancer NYH cells selected for resistance to the bisdioxopiperazine topoisomerase II catalytic inhibitor ICRF-187 demonstrate a functional R162Q mutation in the Walker A consensus ATP binding domain of the alpha isoform.

Bisdioxopiperazine drugs such as ICRF-187 are catalytic inhibitors of DNA topoisomerase II, with at least two effects on the enzyme: namely, locking it in a closed-clamp form and inhibiting its ATPase activity. This is in contrast to topoisomerase II poisons as etoposide and amsacrine (m-AMSA), which act by stabilizing enzyme-DNA-drug complexes at a stage in which the DNA gate strand is cleaved and the protein is covalently attached to DNA. Human small cell lung cancer NYH cells selected for resistance to ICRF-187 (NYH/187) showed a 25% increase in topoisomerase IIalpha level and no change in expression of the beta isoform. Sequencing of the entire topoisomerase IIalpha cDNA from NYH/187 cells demonstrated a homozygous G-->A point mutation at nucleotide 485, leading to a R162Q conversion in the Walker A consensus ATP binding site (residues 161-165 in the alpha isoform), this being the first drug-selected mutation described at this site. Western blotting after incubation with ICRF-187 showed no depletion of the alpha isoform in NYH/187 cells in contrast to wild-type (wt) cells, whereas equal depletion of the beta isoform was observed in the two sublines. Alkaline elution assay demonstrated a lack of inhibition of etoposide-induced DNA single-stranded breaks in NYH/187 cells, whereas this inhibition was readily apparent in NYH cells. Site-directed mutagenesis in human topoisomerase IIalpha introduced into a yeast Saccharomyces cerevisiae strain with a temperature-conditional yeast TOP2 mutant demonstrated that R162Q conferred resistance to the bisdioxopiperazines ICRF-187 and -193 but not to etoposide or m-AMSA. Both etoposide and m-AMSA induced more DNA cleavage with purified R162Q enzyme than with the wt. The R162Q enzyme has a 20-25% decreased catalytic capacity compared to the wt and was almost inactive at <0.25 mM ATP compared to the wt. Kinetoplast DNA decatenation by the R162Q enzyme at 1 mM ATP was not resistant to ICRF-187 compared to wt, whereas it was clearly less sensitive than wt to ICRF-187 at low ATP concentrations. This suggests that it is a shift in the equilibrium to an open-clamp state in the enzyme's catalytic cycle caused by a decreased ATP binding by the mutated enzyme that is responsible for bisdioxopiperazine resistance.

Adenosine Triphosphate↗
PubMed1999

Mutation of a conserved serine residue in a quinolone-resistant type II topoisomerase alters the enzyme-DNA and drug interactions.

A Ser740 --> Trp mutation in yeast topoisomerase II (top2) and of the equivalent Ser83 in gyrase results in resistance to quinolones and confers hypersensitivity to etoposide (VP-16). We characterized the cleavage complexes induced by the top2(S740W) in the human c-myc gene. In addition to resistance to the fluoroquinolone CP-115,953, top2(S740W) induced novel DNA cleavage sites in the presence of VP-16, azatoxin, amsacrine, and mitoxantrone. Analysis of the VP-16 sites indicated that the changes in the cleavage pattern were reflected by alterations in base preference. C at position -2 and G at position +6 were observed for the top2(S740W) in addition to the previously reported C-1 and G+5 for the wild-type top2. The VP-16-induced top2(S740W) cleavage complexes were also more stable. The most stable sites had strong preference for C-1, whereas the most reversible sites showed no base preference at positions -1 or -2. Different patterns of DNA cleavage were also observed in the absence of drug and in the presence of calcium. These results indicate that the Ser740 --> Trp mutation alters the DNA recognition of top2, enhances its DNA binding, and markedly affects its interactions with inhibitors. Thus, residue 740 of top2 appears critical for both DNA and drug interactions.

Amino Acid Substitution↗
PubMed1999

CA 15-3 and c-erbB-2 presence in the saliva of women.

Two markers used to aid in the diagnosis and treatment of breast cancer were examined in the saliva of a cohort of 135 healthy women. The investigators detected the presence of cancer antigen 15-3 (CA 15-3) and c-erbB-2 in the saliva sampled from the 135 women. The marker concentrations for CA 15-3 and c-erbB-2 were also evaluated and compared in terms of tobacco usage, menopausal status, estrogen usage, systemic diseases, prescription medications, race, and age. The results of the study showed no association between the aforementioned variables and salivary marker concentrations. The results of this study establish a baseline for measuring the biomarkers in the saliva of women with no evidence of malignant disease and add further support to the notion that salivary concentrations of CA 15-3 and c-erbB-2 may be useful in the detection of breast cancer and/or the post operative follow-up of patients being treated for carcinoma of the breast.

Adolescent↗
PubMed1999

Oral mucosal permeability and stability of transforming growth factor beta-3 in vitro.

PURPOSE: To investigate the permeability and localization of topically applied 125I-TGF-beta3 in porcine floor-of-mouth mucosa as a function of concentration and exposure. METHODS: The 125I-TGF-beta3 diluted in three different vehicles was applied to the tissue samples mounted in perfusion cells maintained at 37 degrees C. Flux and Kp values were calculated from the perfusate collected over a 24 hour period. The quantity of 125I-TGF-beta3 present in the tissue was determined by horizontal sectioning and subsequent counting. The stability of 125I-TGF-beta3 in saliva and in the tissue was analyzed by SDS polyacrylamide gradient gel electrophoresis. RESULTS: 125I-TGF-beta3 was relatively stable in saliva and in the epithelium; approximately 50% of the total counts in the deeper epithelium were resident in the 25kDa TGF-beta3 homodimer. A steady-state flux was reached approximately 6 hours post application and Kp value was 4.0+/-0.6 x 10(-6) (mean +/- sem). Penetration of 125I-TGF-beta3 to the basal cell layer was concentration dependent but reached nanomolar concentrations even after extensive surface rinsing, representing over one-thousand fold the IC50 for epithelial cell cycle arrest. CONCLUSIONS: The data suggest that topical application of TGF-beta3 to the oral mucosa in an appropriate vehicle can provide effective therapeutic delivery to the tissue.

Absorption↗
PubMed1999

The tomato I-box binding factor LeMYBI is a member of a novel class of myb-like proteins.

The RBCS3A gene of tomato belongs to a small gene family consisting of five members. Although the RBCS1, RBCS2 and RBCS3A promoters contain closely related cis regulatory sequences, the expression patterns of the genes are different. Whereas the RBCS1 and RBCS2 genes are expressed in both leaves and young fruit, the RBCS3A promoter is highly active in leaves, but not in young fruit. This lack of transcription could be due to a mutation in the RBCS3A promoter creating the so-called F-box, a protein binding site located between the activating cis elements, the I-box and G-box. In order to identify proteins that bind to the RBCS3A I-box/F-box region, the yeast one-hybrid system was used. One clone, LeMYBI was isolated which contains strong similarity to plant myb transcription factors. The encoded LeMYBI protein is at least 188 amino acids in length and contains two myb-like domains located at the amino terminus and close to the carboxy terminus, separated by a negatively charged domain. The protein contains a SHAQKYF amino acid signature motif in the second myb-like repeat, which is highly conserved in a number of recently identified plant myb-related genes, thus defining a new class of plant DNA-binding proteins. LeMYBI binds specifically to the I-box sequence of the RBCS1, RBCS2 and RBCS3A promoters, therefore representing the first cloned I-box binding factor. LeMYBI acts as a transcriptional activator in yeast and plants, and binds to the I-box with a DNA-binding domain located in the carboxyterminal domain.

Amino Acid Sequence↗