Across the interface: the hastings heart function clinic.
Explore the source record for details and available documents.
Aged↗
Biomedical subjects
D M Walker
Publications and source records attributed to D M Walker.
Characterization of MTMR3. an inositol lipid 3-phosphatase with novel substrate specificity.
Inositol lipids play key roles in many fundamental cellular processes that include growth, cell survival, motility, and membrane trafficking. Recent studies on the PTEN and Myotubularin proteins have underscored the importance of inositol lipid 3-phosphatases in cell function. Inactivating mutations in the genes encoding PTEN and Myotubularin are key steps in the progression of some cancers and in the onset of X-linked myotubular myopathy, respectively. Myotubularin-related protein 3 (MTMR3) shows extensive homology to Myotubularin, including the catalytic domain, but additionally possesses a C-terminal extension that includes a FYVE domain. We show that MTMR3 is an inositol lipid 3-phosphatase, with a so-far-unique substrate specificity. It is able to hydrolyze PtdIns3P and PtdIns3,5P2, both in vitro and when heterologously expressed in S. cerevisiae, and to thereby provide the first clearly defined route for the cellular production of PtdIns5P. Overexpression of a catalytically dead MTMR3 (C413S) in mammalian cells induces a striking formation of vacuolar compartments that enclose membranous structures that are highly concentrated in mutant proteins.
Animals↗
Mutagenicity at the Hprt locus in T cells of female mice following inhalation exposures to low levels of 1,3-butadiene.
A study was conducted to test the hypothesis that repeated low level exposures to 1,3-butadiene (BD), approaching the OSHA occupational threshold for this chemical, produce a significant mutagenic response in mice. Female B6C3F1 mice (4-5 weeks of age) were exposed by inhalation for 2 weeks (6 h/day, 5 days/week) to 0 or 3 ppm BD, and then necropsied at 4 weeks after the cessation of exposures to measure the frequency of mutations (MF) at the Hprt locus using the T-lymphocyte clonal assay. At necropsy, T cells were isolated from spleen and cultured in the presence of mitogen, growth factors, and a selection agent. Cells were scored for growth on days 8-9 after plating to determine cloning efficiencies (CEs) and Hprt MFs. There was a marginal but significant reduction in the growth of splenic T cells from mice exposed to 3 ppm (n=27) compared with control mice (n=24) (P=0.004), suggesting the occurrence of BD-induced cytotoxicity at this low exposure concentration. In addition, the average Hprt MF in mice exposed to 3 ppm BD [1.54+/-0.82 (S.D.)x10(-6)] was significantly increased by 1.6-fold over the average control value of 0.96+/-0.51 (S.D.)x10(-6) (P=0.004). Comparisons of these data to earlier Hprt mutagenicity studies of mice exposed to high concentrations of BD (where significant mutagenic but not cytotoxic effects were observed) indicate that the ability to detect the cytotoxic and mutagenic responses of T cells to low levels of BD was enhanced by using a much larger sample size than usual for both the control and treatment groups. Additional analyses of the quantitative relationships between CE and MF demonstrated that CE had no significant effect upon MF values in sham-exposed control mice or mice exposed to low-level BD. Furthermore, the approaches for assessing the impact of CE and clonality on Hprt MFs in these control and BD-exposed mice were applied with the same rigor as in in vivo Hprt mutagenicity studies in human children. The overall study results support the conclusion that short-term low-level BD exposure is mutagenic in the mouse.
Administration, Inhalation↗
Calcifying epithelial odontogenic (Pindborg) tumor with malignant transformation and metastatic spread.
BACKGROUND: Pindborg tumors (calcifying epithelial odontogenic tumors) are uncommon neoplasms of odontogenic origin most often located in the posterior mandible. First described in detail in 1955 by Pindborg, these tumors are considered benign but can be locally aggressive in nature, with recurrence rates of 10% to 15% reported. The malignant form of this tumor is exceedingly rare. METHODS: We describe the case of a 64-year-old woman initially treated for a painful infected left mandibular third molar. The patient underwent extraction of the tooth and excision of an associated soft tissue component. Subsequent histologic review identified a Pindborg tumor of the left posterior mandible. RESULTS: After initial excision, this tumor recurred twice, with the recurrences exhibiting a progression to a malignant Pindborg tumor (odontogenic carcinoma) with vascular invasion and spread to a cervical lymph node. Further treatment involved radical surgery and adjuvant radiotherapy. At last review 12 months after treatment, the patient was disease free. CONCLUSIONS: This article describes only the second case of odontogenic carcinoma. The transformation from benign to malignant histologic findings has not previously been documented in this tumor. The salient clinical features of this case are presented along with supportive pathologic and radiologic evidence.
Cell Transformation, Neoplastic↗
Psychiatric residents as CME presenters.
Explore the source record for details and available documents.
Education, Medical, Continuing↗
Psychiatric treatment and operational readiness: clinical guidelines for Air Force practice.
Clinical criteria for psychiatric illnesses that are career limiting to active duty Air Force personnel are defined in Air Force Instruction (AFI) 48-123. The terms used in the AFI are not sufficiently specific to the standards of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). The authors review AFI 48-123 for conditions commonly seen in Air Force mental health practice and offer clinical interpretation of this AFI to bring it into line with DSM-IV. As a result of this synthesis, decisions regarding which mental health conditions warrant medical evaluation board disposition are clearer and more uniform. Clinicians and administrators are encouraged to refer to this paper for assistance in making decisions on mental health patients.
Humans↗
Classical and variant Creutzfeldt-Jakob diseases and their potential impact on the practice of clinical dentistry in Australia.
Following recent published evidence regarding the experimental transmission of prion diseases via blood transfusion, dental practitioners have expressed their concern about the potential impact of these transmissible spongiform encephalopathies on dental care provision. This review provides updated information on Creutzfeldt-Jakob disease and related disorders and highlights their potential significance for the practice of clinical dentistry. The current guidelines in Australia relating to infection control and clinical dental procedures are discussed together with recommended guidelines and considerations from the United Kingdom and the World Health Organization (WHO).
Animals↗
Zidovudine-didanosine coexposure potentiates DNA incorporation of zidovudine and mutagenesis in human cells.
Drug combinations that include nucleoside reverse transcriptase inhibitors (NRTIs) are remarkably effective in preventing maternal-viral transmission of HIV during pregnancy. However, there may be potential long-term risks for children exposed in utero. Examination of the genotoxic and mutagenic effects of two NRTIs, zidovudine [AZT (3'-azido-3'-deoxythymidine)] and didanosine [ddI (2',3'-dideoxyinosine)], in cultured human lymphoblastoid cells revealed multiplicative synergistic enhancement of AZT-DNA incorporation and mutant frequency induction in response to the combined drug exposure, as compared with single-drug exposures. Dose-related increases in DNA incorporation of AZT (as measured by a competitive RIA) and mutagenicity at the HPRT and TK loci (as assessed by cell-cloning assays) were observed in cells exposed in culture to AZT, or equimolar combinations of AZT + ddI, at exposure concentrations ranging from 3 to 30 times the maximum plasma levels found in humans. Because mutagenesis is strongly associated with tumor induction in experimental models, children exposed transplacentally to combinations of NRTIs may be at risk for cancer development later in life.
Anti-HIV Agents↗
Analysis of the amplification refractory mutation allele-specific polymerase chain reaction system for sensitive and specific detection of p53 mutations in DNA.
The sensitivity of the amplification refractory mutation allele-specific polymerase chain reaction system (ARMAS-PCR) to detect known p53 mutations was determined using DNA extracted from two human tumour cell lines collected by cytobrush, as a model for its use in exfoliative cytology. Using DNA extracted from SW480 and CEM cell lines diluted with normal human fibroblasts, a nested ARMAS-PCR was more sensitive than a non-nested version and could detect one mutated cell amongst 100 000 normal cells. When compared with PCR-single stranded conformational polymorphism, nested ARMAS-PCR was 10 000 times more sensitive for detecting mutant p53 in extracted DNA. Primer design proved to be influential on the sensitivity and specificity of the assay; increased specificity was achieved by the use of deliberate mismatches upstream from the 3' end of mutation-specific primers. ARMAS-PCR was confirmed to be specific for the mutation that each primer was designed to detect. Nested ARMAS-PCR offered a rapid and sensitive method of analysis of cells with predetermined p53 mutations and has the potential to be applied to the study of the molecular progression of cancer, including diagnosis and detection of residual disease. It could also be extended to the in situ detection of aberrant cells.
DNA Mutational Analysis↗
Synthesis of highly substituted 5-(trifluoromethyl)ketoimidazoles using a mixed-solid/solution phase motif.
Using a combination of solid phase synthesis for the preparation of N-substituted-N-acylglycines 7 followed by solution-phase ring transformation of trifluoromethylacyl munchnone intermediate 8, a library of 200 trisubstituted-5-trifluoromethylketo (TFMK) imidazoles 9 was prepared. In a sublibrary, bromoacetate resin 4 was treated with 5 amines in parallel to give N-substituted glycines 5 followed by acylation with 12 acid chlorides to provide, upon cleavage from the resin, 60 individual N-substituted-N-acylglycines 7. The glycines 7 were converted to munchnones 8 by treatment with trifluoroacetic anhydride followed by reaction with benzamidine to give trisubstituted-5-TFMK-imidazoles 9. The structural content of the library was analyzed using PlateView of the LCMS results, and individual members were isolated by automated preparative LCMS.
Databases as Topic↗
In situ detection of specific p53 mutations in cultured cells using the amplification refractory mutation system polymerase chain reaction.
Accurate molecular detection of genetic mutations involved in tumorigenesis has been based predominantly on analysis of extracted DNA, but this does not provide detailed information on the location, number, type or clonal distribution of mutated cells and their precise anatomic location and clonal distribution. This study has used a sensitive and specific application of the amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) in situ, combined with in situ hybridization to localize and identify cells with defined p53 mutations. The ARMS-PCR was performed in situ in SW480 cells in suspension and in cells either cultured or cytospun onto glass slides. Amplified mutant DNA PCR products were detected in SW480 cells using digoxigenin-labeled probes, visually identifying cells harboring specific mutations in the p53 gene. In situ hybridization alone of the mutant cells without the amplification step was negative. Normal human fibroblasts or endothelial cells were refractory to in situ amplification. This reaction was mutation-specific as CEM cells with different p53 mutations reacted negatively. Mutant messenger RNA (mRNA) in tumor cells was also selectively amplified in situ by ARMS-PCR following reverse transcription (RT). This study demonstrates the potential of in situ ARMS-PCR or RT-ARMS-PCR for mutation analysis in situ and could have useful clinical applications.
Alleles↗
Relationships between exposure, cell loss and proliferation, and manifestation of Hprt mutant T cells following treatment of preweanling, weanling, and adult male mice with N-ethyl-N-nitrosourea.
Experiments were performed to characterize the age-related patterns of appearance and frequency of hypoxanthine-guanine phosphoribosyl transferase (Hprt) mutant T lymphocytes in thymus and spleen following exposure of preweanling (12-day-old), weanling (22-day-old), and young adult (8-week-old) male B6C3F1 mice to ethylnitrosourea (ENU). Mice were given single i.p. injections of 0 or 40 mg ENU/kg and then groups of animals were necropsied from 2 h to 116 days after treatment to examine the relationships between exposure, cell loss and proliferation, and the frequency of Hprt mutant T cells in thymus and spleen. Hprt mutant frequency (Mf) data for thymus of ENU-exposed (0, 11.7, 35, 58, or 72 mg/kg, or five weekly doses of 1.7 mg/kg i.p.) male C57BL/6 mice (12- or 62-week-old), obtained during an earlier study of spleen cells [I.M. Jones, K. Burkhart-Schultz, C.L. Strout, T.L. Crippen, Factors that affect the frequency of thioguanine-resistant lymphocytes in mice following exposure to ethylnitrosourea, Environ. Mutagen, 9 (1987) 317-329.], were compared to results in B6C3F1 mice. Isolated T cells were cultured in the presence of mitogen, growth factor, and 6-thioguanine to detect Hprt mutants. The time required to achieve maximum Mfs in thymus was uniformly found at 2 weeks after ENU treatment, while the times needed to reach peak values in spleen were proportional to animal age at treatment. These data indicate that age-related differences in the appearance of Hprt mutant cells in spleen are largely defined by the physiologically based, age-dependent trafficking of mutant cells from or through the thymus. Three modes of handling the resulting Hprt Mf data were evaluated: (i) comparing the Mfs at a single time point, (ii) comparing the maximum Mfs observed, and (iii) comparing the change in Mfs over time (or the mutant T cell 'manifestation' curves in treated vs. control mice) in each age group post-exposure. Measuring the Mfs in spleen at multiple time points after cessation of exposure and integrating the frequency of mutants as a function of time appeared to be the superior method for comparing mutagenic responses in different age groups. Some of the underlying assumptions of this approach, as well as its strengths and weaknesses, are discussed.
Age Factors↗
Novel inhibitors of glutamyl-tRNA(Glu) reductase identified through cell-based screening of the heme/chlorophyll biosynthetic pathway.
The metabolite 5-aminolevulinic acid (ALA) is an early committed intermediate in the biosynthetic pathway of heme and chlorophyll formation. In plants, 5-aminolevulinic acid is synthesized via a two-step pathway in which glutamyl-tRNA(Glu) is reduced by glutamyl-tRNA(Glu) reductase (GluTR) to glutamate 1-semialdehyde, followed by transformation to 5-aminolevulinic acid catalyzed by glutamate 1-semialdehyde aminotransferase. Using an Escherichia coli cell-based high-throughput assay to screen small molecule libraries, we identified several chemical classes that specifically inhibit heme/chlorophyll biosynthesis at this point by demonstrating that the observed cell growth inhibition is reversed by supplementing the medium with 5-aminolevulinic acid. These compounds were further tested in vitro for inhibition of the purified enzymes GluTR and glutamate 1-semialdehyde aminotransferase as confirmation of the specificity and site of action. Several promising compounds were identified from the high-throughput screen that inhibit GluTR with an I(0.5) of less than 10 microM. Our results demonstrate the efficacy of cell-based high-throughput screening for identifying inhibitors of 5-aminolevulinic acid biosynthesis, thus representing the first report of exogenous inhibitors of this enzyme.
Aldehyde Oxidoreductases↗
Mutagenicity of 1,3-butadiene at the Hprt locus of T-lymphocytes following inhalation exposures of female mice and rats.
The species specific response to 1,3-butadiene (BD), an important industrial chemical, was investigated by determining the influence of exposure duration and exposure concentration on the mutagenicity of BD in mice and rats and by defining the spectra of mutations in the Hprt gene T-cell mutants from control and BD-exposed mice. Female B6C3F1 mice and F344 rats (4-5 weeks old) were exposed by inhalation to 0, 20, 62.5, or 625 ppm of BD for up to 4 weeks (6 h/day, 5 days/week). Groups of control and exposed animals (n=4-12/group) were necropsied at multiple time points after exposure and the T-cell cloning assay was used to measure Hprt mutant frequencies in lymphocytes isolated from spleen. Mutant clones collected from control and BD-exposed mice were propagated and analyzed by RT-PCR to produce Hprt cDNA for sequencing. In animals necropsied 4 weeks after 2 or 4 weeks of BD exposure (0 or 625 ppm), the rate of accumulation of mutations was greater in mice than in rats. Supra-linear dose-response curves were observed in BD-exposed mice, indicating a higher efficiency of mutant induction at lower concentrations of BD. The mutagenic potency estimates (represented by the differences in the areas under the mutant T-cell 'manifestation' curves of treated vs. control animals) in mice were 11 and 61 following 4 weeks of exposures to 62.5 and 625 ppm of BD, respectively, while mutant frequencies (Mfs) in rats were significantly increased only at 625 ppm BD (mutagenic potency of 7). Molecular analysis of Hprt cDNA from expanded T-cell clones from control and BD-exposed mice demonstrated an increased frequency of mutants in exposed animals that likely contain large deletions in the Hprt gene (P=0.016). These data indicate that both exposure duration and exposure concentration are important in determining the magnitude of mutagenic response to BD, and that mutagenic and carcinogenic properties of BD in mice may be related more to the ability of its metabolites to cause chromosomal deletions than to produce point mutations.
Administration, Inhalation↗
Mutagenicity of the racemic mixtures of butadiene monoepoxide and butadiene diepoxide at the Hprt locus of T-lymphocytes following inhalation exposures of female mice and rats.
The purpose of this study was to determine if Hprt mutant frequency (Mf) data from rodents exposed directly to individual epoxy metabolites of 1,3-butadiene (BD) can be used to identify the relative significance of each intermediate in the mutagenicity of BD in mice vs. rats. To this end, the relative contributions of the racemic mixtures of BD monoepoxide (BDO) and BD diepoxide (BDO(2)) to BD-induced mutagenicity was investigated by exposing mice and rats to selected concentrations of BDO and BDO(2) (i.e., 2.5 and 4.0 ppm, respectively) and comparing the mutagenic potency of each intermediate to that of BD (at 62.5 ppm) when comparable blood levels of metabolites are achieved (in the mouse). Female B6C3F1 mice and F344 rats (4-5 weeks old) were exposed to rac-BDO (0, 2.5, or 25 ppm) or (+/-)-BDO(2) (0, 2, 4 ppm) by inhalation for 4 weeks (6 h/day, 5 days/week), and then groups of control and exposed animals (n=3-12/group) were necropsied at multiple time points post-exposure for measuring Hprt Mfs in splenic lymphocytes (via the T-cell cloning assay) and estimating mutagenic potencies (represented by the difference in the areas under the mutant T-cell 'manifestation' curves of treated vs. control animals). The resulting Mf data, along with the extant metabolism data, suggest that at lower BD exposures (</=62.5 ppm) (+/-)-BDO(2) is a major contributor to the mutagenicity of BD in mice, whereas other metabolites and stereochemical configurations are responsible for mutations in BD-exposed rats and for the incremental mutagenic effects at higher BD exposures in mice. These studies indicate that additional work is needed to determine more definitively the relative contributions of these and other metabolites and stereochemical forms to BD-induced mutagenicity. Also, the novel approach of measuring mutagenic potencies as the change in Hprt Mfs over time in T-cells of exposed vs. control animals, as used in this study, can be valuable for predicting the potential role of these intermediates in each species.
Administration, Inhalation↗
Butenolide endothelin antagonists with improved aqueous solubility.
Continued development around our ETA-selective endothelin (ET) antagonist 1 (CI-1020) has led to the synthesis of analogues with improved aqueous solubility profiles. Poor solubility characteristics displayed by 1 required a complex buffered formulation in order to conduct iv studies. To overcome the use of specific iv formulations for preclinical studies on additional drug candidates, analogues with improved aqueous solubility were desired. Several analogues were synthesized with substitution patterns that allowed for the formation of either acid or base addition salts. These derivatives had dramatically improved aqueous solubility. In addition, these analogues retained equivalent or improved ETA receptor selectivity and antagonist potency, versus 1, both in vitro and in vivo. Compound 29, which contains as a substituent the sodium salt of a sulfonic acid, has an ETA IC50 = 0.38 nM, ETA selectivity of 4200-fold, and ETA functional activity of KB = 7.8, all of which are similar or superior to those of 1. Compound 29 also has vastly superior aqueous solubility and solubility duration, compared to 1. Furthermore, 29 after iv infusion displays improved activity to 1 in preventing acute hypoxia-induced pulmonary hypertension in rats with an ED50 = 0.3 microg/kg/h.
Animals↗
Massive osteolysis of the mandible: report of a case with multifocal bone loss.
Osteolysis of the jaws has been reported in association with infection, cysts, neoplasia, and metabolic, endocrine, or hematologic abnormalities. Rare cases of idiopathic osteolysis have also been recorded. We report the case of a 10-year-old girl with mandibular basal and alveolar bone resorption that has continued over a period of 9 years. The patient has subsequently developed bilateral resorption of the ascending rami and condyles. The maxilla is uninvolved. Investigations included radiology, computerized tomography, scintigraphy, hematology, serum chemistry, endocrinology, histopathology, microbiology, and immunology. Neutrophil chemotaxis, chemiluminescence, and random migration values were low but within the normal range. These findings are interpreted as indicating an unusual variant of massive osteolysis.
Child↗
Regulation of early-endosome dynamics by phosphatidylinositol 3-phosphate binding proteins.
Explore the source record for details and available documents.
Androstadienes↗