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Biomedical subjects

B D Martin

Publications and source records attributed to B D Martin.

15 recordsLinked to original sources
PubMed2001

Nuclear translocation of cytosolic phospholipase A2 is induced by ATP depletion.

Phospholipase A(2) (PLA(2)) enzymes may play a role in cellular injury due to ATP depletion. Renal Madin-Darby canine kidney cells were subjected to ATP depletion to assess the effects of cellular energy metabolism on cytosolic PLA(2) (cPLA(2)) regulation. ATP depletion results in a decrease in soluble cPLA(2) activity and an increase in membrane-associated activity, which is reversed upon restoration of ATP levels by addition of dextrose. In ATP-depleted cells cPLA(2) mass shifts from cytosol to nuclear fractions. GFP-cPLA(2) is localized at the nuclear membrane of stably transfected ATP-depleted LLC-PK(1) cells under conditions where [Ca(2+)](i) is known to increase. cPLA(2) translocation does not occur if the increase in [Ca(2+)](i) increase is inhibited. If [Ca(2+)](i) is allowed to increase when ATP is depleted and the cells are then lysed, cPLA(2) remains associated with nuclear fractions even if the homogenate [Ca(2+)] is markedly reduced. In contrast, cPLA(2), which becomes associated with the nucleus when [Ca(2+)](i) is increased using ionophore, readily dissociates from the nuclear fractions of ATP-replete cells upon reduction of homogenate [Ca(2+)]. Okadaic acid inhibits the ATP depletion-induced association of cPLA(2) with nuclear fractions. Thus energy deprivation results in [Ca(2+)]-induced nuclear translocation, which is partially prevented by a phosphatase inhibitor.

Active Transport, Cell Nucleus↗
PubMed2001

Direct oxidation of guanine and 7,8-dihydro-8-oxoguanine in DNA by a high-valent chromium complex: a possible mechanism for chromate genotoxicity.

Intracellular reductive activation of the human carcinogen chromate, Cr(VI), is a necessary step in the formation of DNA lesions that lead to cancer. Reductive activation forms the transient metastable high-valent oxidation state of Cr(V) as a precursor to the final intracellularly stable oxidation state, Cr(III). In this study, we have used a model high-valent Cr(V) complex, N,N'-ethylenebis(salicylideneanimato)oxochromium(V), Cr(V)-Salen, to probe the mechanism of interaction between this oxidation state of chromium and DNA. This interaction was found to be specific toward the oxidation of the nucleic acid base guanine in unmodified single- and double-stranded oligonucleotides as measured by an increased level of DNA strand cleavage at these sites following piperidine treatment. Replacement of a single guanine residue in DNA with a more readily oxidized 7,8-dihydro-8-oxoguanine (8-oxo-G) base allowed for site-specific oxidation at this modified site within the DNA strand by the Cr(V)-Salen complex. HPLC and ESI-mass spectrometry were used to identify the modified guanine base lesions formed in the reaction of this high-valent chromium complex with the 8-oxo-G-containing DNA substrate. Two of these modified base lesions, identified as guanidinohydantoin and spiroiminodihydantoin, were found in the reaction of the Cr(V)-Salen complex with 8-oxo-G-modified DNA, while only one, spiroiminodihydantoin, was formed from oxidation of the 8-oxo-G nucleoside. A primer extension assay using the exo(-) Klenow fragment demonstrated polymerase arrest at the site of these base modifications as well as a high degree of misincorporation of adenine opposite the site of modification. These results suggest that mutations arising from G --> T transversions would predominate with these lesions. The mechanism of damage and base oxidation products for the interaction between high-valent chromium and DNA described herein may be relevant to the in vivo formation of DNA damage leading to cancer in chromate-exposed human populations. These results also suggest how high-valent chromium can act as a cocarcinogen with 8-oxo-G-forming xenobiotics.

Carcinogens, Environmental↗
PubMed1998

Hypervalent chromium mimics reactive oxygen species as measured by the oxidant-sensitive dyes 2',7'-dichlorofluorescin and dihydrorhodamine.

Intracellular metabolism of the carcinogen chromate [Cr(VI)] produces the oxidative stress and oxidative DNA damage associated with its genotoxicity. Such oxidative stress has previously been measured by fluorescence using oxidant-sensitive dyes and attributed to the formation of reactive oxygen species (ROS). However, metabolism of Cr(VI) also produces Cr(IV) and Cr(V) which can directly damage biological macromolecules without forming ROS. We used the high-valence chromium species, bis(2-ethyl-2-hydroxybutyrato)oxochromate(V) [Cr(V)-EHBA], to test whether high-valence chromium would also react with the oxidant-sensitive dyes 2',7'-dichlorofluorescin (DCFH) and dihydrorhodamine (DHR). Cr(V)-EHBA caused both dyes to fluoresce over a wide dynamic range and under conditions which indicated that Cr(V) had reacted directly with both dyes without first forming a diffusible radical species. Dimethylthiourea (DMTU) and ethanol did not affect Cr(V)-induced fluorescence in vitro or Cr(VI)-induced fluorescence in A549 cells. Under the same conditions, ethanol and DMTU increased the extent of hydrogen peroxide-induced fluorescence. As chromium-induced fluorescence was unaffected by radical scavengers and was qualitatively different from hydrogen peroxide-induced fluorescence, we conclude that DCF and R123 fluorescence in chromate-treated A549 cells is a qualitative and cumulative measure of intracellular Cr(V) formation and not ROS.

Chromium↗
PubMed1998

The management of ear disease: guidelines for Aboriginal health care programs.

Middle ear disease represents a continuing burden of illness for children of circumpolar regions. Uncertainty in management has been shown to create a barrier to timely and adequate treatment. Consistent intervention strategies were sought for the management of middle ear disease in children of the central Canadian Arctic. The current literature was reviewed using MEDLINE. A consensus document was established in consultation with specialists in community medicine, infectious disease, otolaryngology, pediatrics, and community-based care providers. Definitive recommendations and supportive algorithms have been established for management of middle ear disease in Inuit children.

Acute Disease↗
PubMed1998

Prevalence of diabetes mellitus and obesity in the Keewatin District of the Canadian Arctic.

Through a medical chart review, the prevalence of diagnosed diabetes mellitus in Inuit of the Keewatin District of the Canadian Northwest Territories was determined to be 0.27%. All cases were in adults, and no cases of gestational diabetes were noted. The prevalence and pattern of obesity were determined from measurements of body mass index (BMI), skinfold thickness, and waist-hip ratio obtained during the 1990-91 Keewatin Health Assessment Study. Thirty-one percent of 414 randomly identified adults (29% of men, 37% of women) were overweight (BMI > 27). Central fat patterning was more prevalent in women and less prevalent in men from the Keewatin compared to the general Canadian population. Comparison of skinfold thickness values to published measurements obtained from earlier arctic surveys supports the hypothesis that changes in diet and activity levels associated with urbanization have resulted in increased obesity in the Inuit.

Adolescent↗
PubMed1998

Follow-up of a decentralized colposcopy program for the investigation and management of cervical intraepithelial neoplasia in the central Canadian Arctic.

Cervical intraepithelial neoplasia (CIN) is the second leading cause of cancer in Canadian Inuit women, and the incidence ratio in this population is 3.1 times the Canadian average. In 1993 a program was developed in a regional northern health center (Churchill) to provide colposcopy and loop electrosurgery for women in the Keewatin District of the central Canadian Arctic. Data collected prospectively over the following 2.5 years are presented. One hundred and forty-six women were seen in 341 visits. Indication for referral included CIN I on Pap smear (54.1%), CIN II (34.9%), CIN III (9.6%), and carcinoma of the cervix (1.4%). Large loop excision of the transformation zone was performed at a rate of 9.7 procedures per 100 patient visits. Estimated travel cost-savings attributable to this northern program are $299,200 (Canadian). Use of portable colposcopy in patients' home communities is presently being considered in order to provide enhanced accessibility and further cost-effectiveness.

Arctic Regions↗
PubMed1998

Enhancing diagnostic ultrasound programs utilizing wide-area image management technology.

Diagnostic ultrasound in remote sites is limited by attendant delay in interpretation and reporting. Technology advances were incorporated in an ultrasound program based in Churchill, Manitoba, and designed to meet the needs of the Central Canadian Arctic. Still-frame ultrasound images are digitized via a sonographer's picture archiving and communications system (PACS) workstation, and as they are collected they are transmitted over a dial-up Internet protocol network in Dicom 3.0 format to a tertiary care center. Received images are routed to a physician's PACS workstation, where they can be reviewed prior to the patient leaving the remote clinic. The impact of existing technology on a northern ultrasound program is discussed. The implications of technology enhancement are reviewed, with specific reference to remote low bandwidth sites.

Forecasting↗
PubMed1992

Enzymology in monophasic organic media.

Over the past year, an important area of research has been directed towards the fundamental aspects of enzymes and new applications of enzymology in monophasic organic media. Much of this research has focused on the factors that influence enzymatic catalysis in monophasic organic solvents, including the importance of enzyme-associated water, and the effect of organic solvents on enzyme structure and thermodynamic features. From an applications perspective, new advances in the use of enzymes in organic and polymer syntheses and optical resolutions have been made.

Biotechnology↗
PubMed1990

Identification of transcription stop sites at the 5' and 3' ends of the murine adenosine deaminase gene.

We report here the identification and nucleotide sequence of two transcription termination regions associated with the murine adenosine deaminase gene. One region is situated within or very near exon one and in mouse fibroblasts accounts for more than a 50-fold drop in the abundance of nascent transcripts. This termination region is believed to be involved in the regulation of adenosine deaminase gene transcription. The other termination region is located approximately 3.5 kilobases beyond the major polyadenylation site and defines the 3' boundary of the adenosine deaminase transcription unit.

Adenosine Deaminase↗
PubMed1990

Coenzyme AdoB12 vs AdoB12.-homolytic Co-C cleavage following electron transfer: a rate enhancement greater than or equal to 10(12).

Comparison of the 25 degrees C Co-C bond homolysis rate constant of adenosyl-cobalamin (coenzyme B12) vs that for electrochemically reduced adenosyl-cobalamin radical anion indicates a rate enhancement of at least 10(12 +/- 2) upon the addition of one antibonding electron. Even though electrochemical reduction promotes Co-C homolysis by virtually the same amount as the 10(12 +/- 1) enzymic activation seen for adenosylcobalamin, electron-transfer activation of the Co-C homolysis in adenosylcobalamin-dependent enzyme reactions is considered unlikely, based on four lines of evidence.

Cobamides↗
PubMed1990

Structural and functional analysis of the murine adenosine deaminase gene.

We describe the structural and functional analysis of cosmid clones that span the entire murine adenosine deaminase gene. Functional analysis indicated that these clones are capable of encoding murine adenosine deaminase activity when introduced into human cell lines. Structural analysis revealed that the gene consists of 12 exons distributed over approximately 25 kb. The exact size of each exon and the sequence of each exon/intron junction were determined. The results show that the 1056-nucleotide open reading frame for adenosine deaminase extends from exon 1 to exon 11, and that exon 12 contains untranslated sequences only. During the course of these investigations, we discovered that a gene encoding an abundant 1.3-kb polyadenylated transcript overlaps the 3' end of the murine adenosine deaminase gene and is transcribed from the opposite strand.

Adenosine Deaminase↗
PubMedDate not supplied

Diffusion and transfer of antibody proteins from a sugar-based hydrogel.

Diffusion of antibody protein from hydrogel films and hydrogel encapsulated in a microcapillary was studied. Thin hydrogel films were formed by crosslinking 6-acryloyl-B-O-methylgalactoside with N,N'-methylene-bis-acrylamide and the diffusive transport of monoclonal antimouse IgG-FITC into and out of the hydrate films was measured. Diffusion coefficients in 2 and 4% crosslinked hydrogel films were measured. The measured diffusion constants determined for IgG in both the 2 and 4% hydrogel films were comparable to the free diffusion of IgG in bulk water (Dmean approximately 10(-7) cm2/s). In addition, 2% crosslinked hydrogels were prepared in a capillary tube and the transport of antimouse IgG-FITC into and out of the hydrated hydrogel was measured. Kinetic analysis indicated that the protein transport through the capillary hydrogel was faster than would be expected for a simple diffusion process. Finally, by utilizing the diffusion of antibody from the capillary hydrogel, transfer of antibody to a silica surface was demonstrated. A capillary hydrogel loaded with antimouse IgG-FITC was used to transfer the protein to a silica surface forming a 30-micron spot of antibody, which was imaged using fluorescence microscopy. These results may lead to the development of a nonlithographic method of patterning antibodies on surfaces for use in integrated microimmunosensors.

Acrylamides↗
PubMedDate not supplied

Highly swelling hydrogels from ordered galactose-based polyacrylates.

High swelling galactose-based hydrogels have been prepared using a chemoenzymatic procedure. Regioselective acylation of beta-O-methyl-galactopyranoside in nearly anhydrous pyridine with lipase from Pseudomonas cepacia yields the 6-acryloyl derivative (Compound I). Further lipase-catalysed acylation of the monoacrylate derivative in nearly anhydrous acetone yielded 2,6-diacryloyl-beta-O-methyl galactopyranoside (Compound II) that can act as a cross-linker with a structure similar to that of the sugar-based monomer. The high selectivity of enzyme catalysis yielded apparently highly regular hydrogel networks with swelling ratios at equilibrium ranging from 170 to 1100. elastic moduli ranging from 0.005 to 0.088 MPa and calculated mesh sizes ranging from 1160 to 6600 A. These values are far higher than conventional uncharged or lightly charged hydrogels at similar elastic moduli. Gel swelling was fast, with 75% of the equilibrium swelling value reached in a fractional time of 0.17. Non-selective chemical acryloylation of beta-O-methyl galactopyranoside followed by polymerization yielded a far lower-swelling hydrogel than that obtained using selective enzyme catalysis. These results indicate that the highly regular polymer structure achieved by regioselective enzyme-catalysed acylation yields relatively strong and highly swellable materials. Sugar-based hydrogels, such as those described herein, may find particular use as biomaterials because of their high water content, homogeneity, stability and expected non-toxicity. A wide range of pore sizes can be attained, suggesting that they may also be especially useful as matrices for enzyme immobilization and controlled delivery of biological macromolecules.

Absorption↗