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Biomedical subjects

N R Smith

Publications and source records attributed to N R Smith.

17 recordsLinked to original sources
PubMed2000

Vertebrate pseudogenes.

Pseudogenes are commonly encountered during investigation of the genomes of a wide range of life forms. This review concentrates on vertebrate, and in particular mammalian, pseudogenes and describes their origin and subsequent evolution. Consideration is also given to pseudogenes that are transcribed and to the unusual group of genes that exist at the interface between functional genes and non-functional pseudogenes. As the sequences of different genomes are characterised, the recognition and interpretation of pseudogene sequences will become more important and have a greater impact in the field of molecular genetics.

Animals↗
PubMed2000

Morphologic characterization of the ice worm Mesenchytraeus solifugus.

Ice worms occupy a unique position in metazoan phylogeny in that they are the only known annelid that completes its life cycle in ice. The mechanism(s) associated with this adaptation are likely to occur at different levels, ranging from modification of their metabolism to changes in morphology. In this study, we examined specimens of Mesenchytraeus solifugus by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in an effort to identify morphologic structures that may aid in its glacial habitation. We report that M. solifugus contains an elongated head pore at the tip of its prostomium, numerous sensory structures, and differentially oriented setae that curve abruptly at their distal end.

Alaska↗
PubMed1997

Rapid determination of the complexity of cDNA bands extracted from DDRT-PCR polyacrylamide gels.

A band extracted from a differential display polyacrylamide gel often represents a composite of heterogeneous products. We have developed a non- radioactive method to simply and rapidly analyse its complexity. A fluorescent restriction enzyme fingerprint of the composite mixture is generated. The number of individual bands observed in this fingerprint indicates the complexity of the re-amplified cDNA mixture. Restriction fingerprints of the inserts of cDNA subclones derived from the re-amplified cDNA mixture are compared to the composite fingerprint to select those representing the most intense bands in the composite. This dramatically reduces the number of clones required for further characterisation.

Base Sequence↗
PubMed1997

Common BRCA1 variants and susceptibility to breast and ovarian cancer in the general population.

Most multiple case families of young onset breast cancer and ovarian cancer are thought to be due to highly penetrant mutations in the predisposing genes BRCA1 and BRCA2. However, these mutations are uncommon in the population and they probably account for only a few percent of all breast cancer incidence. A much larger fraction of breast cancer might, in principle, be due to common variants which confer more modest individual risks. There are several common polymorphisms in the BRCA1 gene which generate amino acid substitutions. We have examined the frequency of four of these polymorphisms: Gln356Arg, Pro871Leu, Glu1038Gly and Ser1613Gly in large series of breast and ovarian cancer cases and matched controls. Due to strong linkage disequilibrium, these four sites generate only three haplotypes with a frequency > 1.3%. The most common haplotypes, defined by the alleles Gln356Pro871Glu1038Ser1613 and Gln356Leu871Gly1038Gly1613, have frequencies of 0.57 and 0.32 respectively, and these frequencies do not differ significantly between patient and control groups. Thus the most common polymorphisms of the BRCA1 gene do not make a significant contribution to breast or ovarian cancer risk. However, our data suggest that the Arg356 allele may have a different genotype distribution in breast cancer patients from that in controls (Arg356 homozygotes are more frequent in the control groups, P = 0.01), indicating that it may be protective against breast cancer. If this finding can be confirmed, it may provide an insight into the structural features of the BRCA1 protein that are important for its function.

Adult↗
PubMed1997

Automated differential display using a fluorescently labeled universal primer.

We have modified the automated differential display reverse transcription polymerase chain reaction technique (DDRT-PCR) such that a single fluorescently labeled universal primer (d(F)CTCACG-GATCCGTCGATTTT) is used in all PCRs together with a selection of arbitrary primers. We term this fluorescent detection procedure FDDRT-PCR. Anchoring primers of general structure dTGGTCTCACGGATCCTCGA-(T)12 VN (where N can be any deoxynucleoside and V can be any deoxynucleoside other than thymidine) are used for the RT step, and the universal primer together with selected arbitrary primers are then used for the PCR amplification. Advantages of this approach are: (i) the fluorescently labeled universal primer is a constant feature in every PCR, so that changes in banding profile are highly likely to reflect the incorporation of different arbitrary 10-mer primers; (ii) artifacts that result from arbitrary 10-mer to arbitrary 10-mer primer amplifications are not observed by fluoresence detection on an automated gene scanner because such products are not fluorescently labeled; (iii) sample throughput and ease of data handling are increased when compared with the conventional radioactive/manual approach and (iv) using a single fluorescently labeled primer in all PCRs is highly cost-effective.

Autoradiography↗
PubMed1996

Bioavailability of selenium accumulated by selenite-reducing bacteria.

The bioavailability of selenium (Se) was determined in bacterial strains that reduce selenite to red elemental Se (SeO). A laboratory strain of Bacillus subtilis and a bacterial rod isolated from soil in the vicinity of the Kesterson Reservoir, San Joaquin Valley, CA, (Microbacterium arborescens) were cultured in the presence of 1 mM sodium selenite (Na2SeO3). After harvest, the washed, lyophilized B. Subtilis and M. arborescens samples contained 2.62 and 4.23% total Se, respectively, which was shown to consist, within error, entirely of SeO. These preparations were fed to chicks as supplements to a low-Se, vitamin E-free diet. Three experiments showed that the Se in both bacteria had bioavailabilities of approx 2% that of selenite. A fourth experiment revealed that gray SeO had a bioavailability of 2% of selenite, but that the bioavailability of red SeO depended on the way it was prepared (by reduction of selenite). When glutathione was the reductant, bioavailability resembled that of gray SeO and bacterial Se; when ascorbate was the reductant, bioavailability was twice that level (3-4%). These findings suggest that aerobic bacteria such as B. subtilis and M. arborescens may be useful for the bioremediation of Se-contaminated sites, i.e., by converting selenite to a form of Se with very low bioavailability.

Animals↗
PubMed1995

Physiological mechanisms regulating the conversion of selenite to elemental selenium by Bacillus subtilis.

We have demonstrated that the common soil bacterium, Bacillus subtilis, reduces selenite to an insoluble and much less toxic product--the red form of elemental selenium. Reduction was effected by an inducible system that appears to deposit elemental selenium between the cell wall and the plasma membrane. Glucose and sucrose supported selenite reduction. Although malate and citrate supported growth, no significant reduction of selenite occurred, indicating the importance of the redox state of the culture substrate. Selenite reduction in the millimolar concentration range (i.e., cultures supplemented with 1 mM selenite) was not affected by a ten-fold excess of nitrate or sulfate--compounds that serve as alternate electron acceptors and antagonize selenite reduction by anaerobic bacteria. Similarly, nitrite and sulfite did not significantly affect the rate or extent of selenite reduction. B.subtilis was able to grow and produce selenium (Se degree) at selenite concentrations ranging from 0.6 microM to 5 mM (50 ppb to 395 ppm selenium). At the lowest selenite concentration tested, 50 ppb selenium, B.subtilis removed 95% of the selenite from the liquid phase. The results suggest that selenite is reduced via an inducible detoxification system rather than dissimilatory electron transport. The findings establish the potential utility of B.subtilis for the bioremediation of selenite-polluted sites.

Bacillus subtilis↗
PubMed1991

A comparison of three bracket bases: an in vitro study.

The purpose of this study was to evaluate the differences in mean tensile bond strength between three groups of orthodontic bracket bases; coarse mesh (Dentaurum), fine mesh (A-Company), and an undercut base (Dynalok). Due to microscopic differences seen in the course mesh bases, these were further sub-divided into rough, smooth, and defective mesh groups, and tested in a double blind trial. All brackets were bonded to plastic cylinders with a highly filled composite resin (Concise) and tested to failure on an Instron universal testing machine. No significant differences in mean tensile bond strength were seen between the rough, smooth, and defective coarse mesh bases. The fine mesh base showed significantly higher mean tensile bond strength compared with the coarse. Both meshes performed significantly better than the undercut base.

Acrylic Resins↗
PubMed1987

Characterization of the binding of Pseudomonas aeruginosa alginate to human epithelial cells.

The alginate produced by Pseudomonas aeruginosa has been reported to play a role in the adhesion of this bacterium to epithelial cell surfaces, although some controversy concerning this role exists. To clarify this controversy, we investigated the ability of alginate to bind to human buccal epithelial cells (BECs) and human tracheal epithelial cells (TECs). Alginate from P. aeruginosa 492c bound to both BECs and TECs. Alginate from strain 492c was found to be multivalent and thus capable of agglutinating both BECs and TECs. The multivalency of alginate complicated the determination of the number of alginate-specific receptors on the BEC and the apparent association constant (Ka). By using the analysis of Hogg and Winzor (Biochim. Biophys. Acta 843:159-163, 1985), an average valency of 2.6 BEC binding domains per alginate molecule was determined, and the maximum binding capacity per BEC was calculated to be 5.8 X 10(-4) micrograms, with a Ka of 4.1 X 10(-2) ml/micrograms. The binding of alginate to immobilized BECs (where only 50% of the BEC surface is exposed) yielded values of 2.52 X 10(-4) micrograms of alginate per BEC for the maximum binding capacity per BEC and a Ka of 3.30 X 10(-2) ml/micrograms. The alginate-specific site on the BEC surface was trypsin sensitive. Alginate from P. aeruginosa 492a did not bind to BECs, differing substantially from that of strain 492c. The data presented here demonstrate that alginate purified from some strains of P. aeruginosa may bind to TECs and BECs in a defined, specific manner, whereas alginate from other strains does not, reflecting structural diversity in P. aeruginosa alginates.

Adhesins, Bacterial↗
PubMed1986

The relationships between volition, activity pattern, and life satisfaction in the elderly.

This study examines the relationships between the volition subsystem, activity pattern, and life satisfaction of 60 elderly individuals. The volition subsystem includes an individual's interests, values, and personal causation. The Occupational Questionnaire (OQ) was developed to measure volition subsystems and activity patterns, and it was pilot tested for reliability and validity. Scores on the OQ were compared with measures of subjects' life satisfaction. Results of the study identified several aspects of the subjects' occupations that were related to their level of life satisfaction. The most important findings were the positive correlations between the degree of interest, value, and personal causation in occupation and life satisfaction. Time spent in work and leisure was found to be correlated more highly with high levels of life satisfaction than was time spent in daily living tasks and rest. Although further verification of these results is needed, these findings indicate that occupational therapists may enhance the life satisfaction of their elderly patients by emphasizing interests, values, personal causation, work, and leisure in their treatment programs.

Aged↗
PubMed1978

An x-ray microanalysis study of differences in concentration of elements in brain cells due to opiates, cell type, and subcellular location.

Adult female Sprague Dawley rats were divided into three groups and given two daily doses of: 1) morphine (25 mg/kg at each injection), or 2) methadone (5 mg/kg), or 3) saline for nine days. Two hours before the rats were killed on day 10, they were given a double dose of the drugs. Fifteen minutes before being killed, some of the morphine-treated rats were given the opiate antagonist naloxone (2.5 mg/kg), which caused a sudden arousal in these rats. At the time of killing, the preoptic-hypothalamic region was repidly removed and frozen in liquid propane to prevent translocation of elements in cells. Frozen 4-micrometer sections were cut, freeze-dried, and electron-probed in a scanning electron microscope, and energy-dispersive x-ray spectra were collected. The characteristic peak-to-continuum ratio for all detectable elements was determined in both the nucleus and the cytoplasm of ependymal cells and neurons. The data from nine cells of each type in each rat brain were then subjected to one- and three-way analysis of variance. The results show significant differences in the distribution of elements (sodium, magnesium, phosphorus, sulfur, chlorine, potassium, and calcium) which are dependent upon: 1) subcellular localization, 2) cell type, and particularly, 3) opiate treatment. The behavioral state produced by the opiates is correlated with the effects they have on intracellular concentration of several elements, most notably, sodium.

Animals↗
PubMed1977

Concentration of elements in mitotic chromatin as measured by x-ray microanalysis.

Unfixed frozen-dried and uncoated tissue sections of the mouse duodenum were placed on carbon planchets and analyzed in a scanning electron microscope fitted with energy dispersive X-ray equipment. Computer analysis of the X-ray spectra allowed elemental microanalysis of the nucleus, cytoplasm, and mitotic chromatin regions in the cryptal and villus enterocytes. The peak to continuum ratio of S, Cl, K, and Ca were higher in mitotic chromatin than any of the other sites measured. The redistribution of Ca at mitosis is postulated to help explain both chromosome condensation and assembly of the mitotic spindle apparatus.

Animals↗