Biomedical subjects
K A Russell
Publications and source records attributed to K A Russell.
Peroxisomal targeting, import, and assembly of alcohol oxidase in Pichia pastoris.
Alcohol oxidase (AOX), the first enzyme in the yeast methanol utilization pathway is a homooctameric peroxisomal matrix protein. In peroxisome biogenesis-defective (pex) mutants of the yeast Pichia pastoris, AOX fails to assemble into active octamers and instead forms inactive cytoplasmic aggregates. The apparent inability of AOX to assemble in the cytoplasm contrasts with other peroxisomal proteins that are able to oligomerize before import. To further investigate the import of AOX, we first identified its peroxisomal targeting signal (PTS). We found that sequences essential for targeting AOX are primarily located within the four COOH-terminal amino acids of the protein leucine-alanine-arginine-phenylalanine COOH (LARF). To examine whether AOX can oligomerize before import, we coexpressed AOX without its PTS along with wild-type AOX and determined whether the mutant AOX could be coimported into peroxisomes. To identify the mutant form of AOX, the COOH-terminal LARF sequence of the protein was replaced with a hemagglutinin epitope tag (AOX-HA). Coexpression of AOX-HA with wild-type AOX (AOX-WT) did not result in an increase in the proportion of AOX-HA present in octameric active AOX, suggesting that newly synthesized AOX-HA cannot oligomerize with AOX-WT in the cytoplasm. Thus, AOX cannot initiate oligomerization in the cytoplasm, but must first be targeted to the organelle before assembly begins.
Validating an uncoupled laser-aiming device for serial implant radiography.
Precision of bone level measurements adjacent to implants in longitudinal studies is, in part, dependent on the accurate reproduction of the relationships of the central x-ray beam, object, and film. The purpose of this study was to test the precision of a prototype aiming device consisting of three laser pointers symmetrically mounted on an x-ray cone, a ring supporting three mirrors aligned to reflect the laser light onto a grid on the x-ray head, and a custom film holder to align the film with the implant and the mirrors. Multiple regression analysis revealed a very high correlation between the angular change of the central ray and the position of the reflected light beam (R2 = 0.999, sig. < 0.001). Precision of the aiming device was determined from measurements made on digitized serial radiographs, exposed by two operators, of three dental implants in dried mandibles. The interthread distances and thread widths on each radiograph were measured using the NIH Image program. Chi-square tests demonstrated that the clinical use of the aiming device was independent of the operators and clinically applicable in all areas of the jaw. These tests also revealed that the significant errors found were directly related to the measurement of the thread width. This indicates a measurement technique problem rather than a deficiency with the aiming device. Additionally, none of the errors was greater than 0.032 mm, which is less than the accepted standard of 0.2 mm annual bone loss, and therefore should not be clinically significant. These results support the feasibility of using a three-beam reflected-light aiming device for precision of x-ray geometry in serial studies.
The Pichia pastoris PER6 gene encodes the yeast homologue of human PAF-1.
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Characterization of the molecular defect in a null allele of the opaque-2 locus of maize.
The molecular defect in an opaque-2 (o2) mutant, previously characterized as a null allele, has been identified as containing an insertion of the transposable element of the Bergamo (Bg) family. Restriction mapping and partial sequence analysis of the Bg in the o2 null allele indicates that this element is distinct from the previously described Bg as well as the defective Bg (rbg) of the o2m(r) allele. It is, however, inserted at the same site in O2 as the rbg of o2m(r) and can transpose when Bg is present. This study shows that, depending on genetic background, this allele may not behave as a stable null which could dramatically influence the conclusions drawn from experiments based on this particular mutant.
Orthodontic treatment in the mixed dentition.
In the mixed dentition, the goal of orthodontic treatment is to maintain or improve arch integrity for the eruption of the permanent teeth, and to prevent the development of a more complicated malocclusion. The importance of correct diagnosis prior to the treatment of mixed-dentition patients cannot be over emphasized. An understanding of the mixed dentition's normal development allows clinicians to determine if the occlusion is developing outside of the normal range. Appropriate treatment can only be planned after this determination has been made. Once it is concluded that orthodontic treatment is required, decisions must be made regarding the timing of treatment, the specific type of treatment needed, and the provider of treatment. By employing a systematic approach to examination and treatment planning, the general dental practitioner can provide an important service to patients with a mixed dentition.
PER3, a gene required for peroxisome biogenesis in Pichia pastoris, encodes a peroxisomal membrane protein involved in protein import.
PER genes are essential for the biogenesis of peroxisomes in the yeast Pichia pastoris. Here we describe the cloning of PER3 and functional characterization of its product Per3p. The PER3 sequence predicts that Per3p is a 713-amino acid (81-kDa) hydrophobic protein with at least three potential membrane-spanning domains. We show that Per3p is a membrane protein of the peroxisome. Methanol- or oleate-induced cells of per3-1, a mutant strain generated by chemical mutagenesis, lack normal peroxisomes but contain numerous abnormal vesicular structures. The vesicles contain thiolase, a PTS2 protein, but only a small portion of several other peroxisomal enzymes, including heterologously expressed luciferase, a PTS1 protein. These results suggest that the vesicles in per3-1 cells are peroxisomal remnants similar to those observed in cells of patients with the peroxisomal disorder Zellweger syndrome, and that the mutant is deficient in PTS1 but not PTS2 import. In a strain in which most of PER3 was deleted, peroxisomes as well as peroxisomal remnants appeared to be completely absent, and both PTS1- and PTS2-containing enzymes were located in the cytosol. We propose that Per3p is an essential component of the machinery required for import of all peroxisomal matrix proteins and is composed of independent domains involved in the import of specific PTS groups.
Pericentric inversion of chromosome 16 in a large kindred: spectrum of morbidity and mortality in offspring.
Constitutional pericentric inversions of chromosome 16 are rare in the general population. We report here a large kindred who carry an inv(16)(p13q22) rearrangement. In general, individuals with the inv(16) are in good health but prone to reproductive loss. Two different types of recombinant offspring were identified in this family and analyzed at the molecular level using probes from the alpha-globin and polycystic kidney disease loci. Both were associated with serious major malformations.
Satisfaction of recent University of British Columbia dietetics graduates with undergraduate education and current job.
This study was designed to investigate the career status of recent University of British Columbia (UBC) dietetics graduates and their satisfaction with undergraduate education and current job. All graduates from the UBC Dietetics Program between 1978-1987, inclusive (n = 238), were mailed questionnaires. Information was sought regarding success in obtaining a dietetic internship, current employment status, job satisfaction, and satisfaction with undergraduate education. Questionnaires were returned by 67% (n = 130) of those who received them. Approximately 83% were eventually successful in obtaining an internship. Most respondents (68.5%) were employed as dietitian/nutritionists, and 69% of those who were employed worked full-time. Those who interned had significantly higher salaries than those who did not. A measure of overall job satisfaction revealed that 89.6% were satisfied to very satisfied with their present job, and scores on the Brayfield-Rothe Index of Job Satisfaction revealed no differences between those who did and did not intern. With regard to undergraduate education, respondents were most satisfied with library resources, class size and quality of teaching, and least satisfied with internship opportunities. Those who had interned were significantly more satisfied with their undergraduate education than were those who had not. We conclude that success in obtaining a dietetic internship affects salary and satisfaction with undergraduate education, but does not affect job satisfaction.
The effects of tricaine methanesulfonate (MS-222) on plasma nonesterified fatty acids in rainbow trout, Oncorhynchus mykiss.
The effects of tricaine methanesulfonate (MS-222), a commonly used fish anesthetic, on plasma nonesterified fatty acid levels (NEFA) were examined in rainbow trout, Oncorhynchus mykiss. Total NEFA levels declined with increasing duration of exposure to MS-222. Most of the decline in total NEFA was due to decreases in saturated fatty acids (14:0, 16:0 and 18:0). The fatty acid displaying the most rapid response to exposure to MS-222 was 20:5n-3. The lower plasma NEFA levels in anesthetized fish may be explained by depressed lipolysis in the presence of the anesthetic.
Gorlin-Goltz: what's in a name?
This paper describes the clinical features of two very distinct syndromes with similar names: Gorlin-Goltz and Goltz-Gorlin Syndromes. A case report is presented that highlights the differences between these syndromes. To avoid errors in diagnosis because of the similarity in names, the authors caution that, based on additional information now available, the preferred names should be Focal Dermal Hypoplasia syndrome for Goltz-Gorlin syndrome and Nevoid Basal Cell Carcinoma syndrome for Gorlin-Goltz syndrome.