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J M Wright

Publications and source records attributed to J M Wright.

At least 55 records · Page 3Linked to original sources
PubMed1999

A 59 amino acid insertion increases Ca(2+) sensitivity of rbslo1, a Ca2+ -activated K(+) channel in renal epithelia.

We previously cloned a MaxiK channel alpha-subunit isoform, rbslo1, from rabbit kidney with an amino acid sequence highly homologous to mslo but with a 59 amino acid insertion between S8 and S9 (Morita et al., 1997. Am. J. Physiol. 273:F615-F624). rbslo1 activation properties differed substantially from mslo with much greater Ca2+ sensitivity, half-activation potential of -49 mV in 1 micron m Ca2+. We now report single-channel analysis of rbslo1 and delA, a construct produced by removal of the 59 amino acid insertion at site A. delA is identical to mslo from upstream of S1 to downstream of S10 with the exception of 8 amino acids. Slope of the steady-state Boltzmann voltage activation curve was 8.1 mV per e-fold change in probability of opening for both rbslo1 and delA. The apparent [Ca2+](i) properties in delA were more like mslo but the voltage-activation properties remained distinctly rbslo1. Ca2+ affinity decreased and transmembrane voltage effects on apparent Ca2+ affinity increased in delA. The differences between rbslo1 and other cloned channels appear to be localized at insertion site A with both the insertion sequence and amino acid substitutions near site A being important. The steeper activation slope makes the channel more responsive to small changes in transmembrane voltage while the insertion sequence makes the channel functional at physiological low levels of [Ca2+](i).

Amino Acid Sequence↗
PubMed1999

Idiopathic scoliosis. The clinical value of radiologists' interpretation of pre- and postoperative radiographs with interobserver and interdisciplinary variability.

STUDY DESIGN: A retrospective analysis of radiographic reports of 161 consecutive patients with idiopathic scoliosis at the authors' institution. OBJECTIVES: To compare various radiographic findings that directly affect surgical decision-making and the evaluation of postsurgical outcomes to determine the usefulness of information gathered from radiologists' multiple duplicate reading of films. SUMMARY OF BACKGROUND DATA: To the authors' knowledge, there are no previous studies on the readings of scoliosis films by radiologists and surgeons. METHODS: The patient pool was drawn from the private practices of two board-certified orthopaedic surgeons. Each set of radiographs was read by one of seven board-certified radiologists and by one of the two surgeons. The two reports of each radiograph were compared. The factors included in the reports were scoliosis deformity, scoliosis type, curve progression, curve magnitude, levels of the curve, kyphosis, lordosis, the presence of instrumentation, and the presence of a fusion. RESULTS: The radiologists and orthopedic surgeons mentioned the presence of scoliosis in 95% and 99.4% of their reports, respectively. The type of scoliosis was mentioned in 5% of reports by radiologists and in 99.4% by orthopedists. Progression of the curve was documented in 16.7% of the radiologists' reports and in 98.4% of orthopedists' reports. The magnitude of the curve was stated in 12.6% of the radiologists' reports, compared with 98.1% of the orthopaedists' reports. The levels of the curve were documented in 10.6% and 95.6% of reports by the radiologists and orthopedists, respectively. Radiologists mentioned kyphosis and lordosis in 28% and 26.5% of reports, respectively. These same two entities were mentioned in 98.2% and 79.4% of reports by the orthopedists. Finally, the radiologists noted the presence of instrumentation and of a fusion in 77.8% and 68.3% of reports, respectively. Orthopedists mentioned these same two entities in 84.4% and 100% of reports, respectively. In the radiologists' reports on the presence of instrumentation, 20% were mislabeled or improperly identified. Seven percent of the fusions documented by the radiologists were incorrect because they were recorded before biologic fusion could have taken place. In all these categories, the radiologists provided information in excess of the orthopedic reports a total of 1.9% of the time. Of this 1.9% additional information, 36.8% was incorrectly read or mislabeled. The other 63.2% of the additional information (1.9% of the total) did not elucidate anything of real clinical significance that was missed by the orthopedic surgeons (e.g., a tumor in the lung). CONCLUSIONS: These findings show that the attending orthopedic spine surgeons gained little useful information from the radiologists' multiple duplicate reading of films.

Humans↗
PubMed1999

A LINE2 repetitive DNA sequence from the cichlid fish, Oreochromis niloticus: sequence analysis and chromosomal distribution.

We report the cloning and characterization of a long interspersed nucleotide element (LINE) from a cichlid fish, Oreochromis niloticus, and show the distribution of this element, called CiLINE2 for cichlid LINE2, in the chromosomes of this species. The identification of an open reading frame in CiLINE2 with amino acid sequence similarity to reverse transcriptases encoded by LINE-like elements in Caenorhabditis elegans, Platemys spixii, Schistosoma mansoni, Gallus gallus (CRI), Drosophila melanogaster (I factor), and Homo sapiens (LINE2), as well as the structure of the element, suggest it is a member of this family of non-long terminal repeat-containing retrotransposons. Search of a DNA sequence database identified sequences similar to CiLINE2 in four other fish species (Haplotaxodon microlepis, Oreochromis mossambicus, Pseudotropheus zebra, and Fugu rubripes). Southern blot hybridization experiments revealed the presence of sequences similar to CiLINE2 in all Tilapiini species analyzed from the genera Oreochromis, Tilapia, and Sarotherodon, and gave an estimated copy number of about 5500 for the haploid genome of O. niloticus. Fluorescent in situ hybridization showed that CiLINE2 sequences were organized in small clusters dispersed over all chromosomes of O. niloticus, with a higher concentration near chromosome ends. Furthermore, the long arm of chromosome 1 was strikingly enriched with this sequence. The distribution of LINE2-related elements might underlie the difference in chromosome banding patterns observed between cold-blooded vertebrates and mammals.

Amino Acid Sequence↗
PubMed1999

Microsatellite DNA analysis of population structure in Atlantic herring (Clupea harengus), with direct comparison to allozyme and mtDNA RFLP analyses.

Previous attempts to test for small-scale stock structuring within Atlantic herring (Clupea harengus L.) with molecular markers have been hampered by uninformative levels of genetic variation. Here we report the first application of microsatellite DNA markers to investigate population subdivision in Atlantic herring from Norwegian waters and the Barents Sea, and also examine microsatellite differentiation between C. harengus and Pacific herring (C. pallasi). Results from four microsatellite loci indicate high, and informative, variation compared to molecular markers used previously: number of alleles per locus=18-41; mean expected heterozygosity within samples=0.90-0.93. Significant genetic differences were detected between almost all samples representing postulated Icelandic summer-spawner, Norwegian spring-spawner and Norwegian fjord stocks, using Fisher's exact test, FST and RST values. Levels of allele frequency differentiation between Atlantic and Pacific herring overlapped the range seen among Atlantic herring samples, indicating that microsatellites are poor indicators of the degree of species differentiation. Comparison with allozyme and mitochondrial DNA restriction fragment length polymorphism (RFLP) datasets from the same samples suggests that microsatellites may detect structuring at a finer scale, but are less informative at larger scales of divergence.

Animals↗
PubMed1999

Evaluation of the use of calendar blister packaging on patient compliance with STD syndromic treatment regimens.

BACKGROUND: Good compliance with antibiotic therapy is critical for successful management of sexually transmitted diseases (STDs). GOAL OF THIS STUDY: To evaluate the use of user-friendly drug packaging as a means of improving patient compliance with STD therapy and the acceptability of the packaging. STUDY DESIGN: Compliance of patients with STDs with treatment regimens for three different STD syndromes, using antibiotics packed in standard medicine packaging (SP), was compared to that of patients using calendar blister packaged drugs. Compliance was measured by counting the remaining pills at two return visits. Questionnaires were used to evaluate acceptability of the packs. RESULTS: Compliance was significantly better among patients using the calendar blister packs than among those using standard packs, irrespective of dosing frequency. The degree of poor compliance increased with increasing dosing frequency. There was a high level of satisfaction with the blister pack among patients and health care workers. CONCLUSION: Compliance can be improved by the introduction of user-friendly drug packaging, especially for more complex dosing regimens.

Adult↗
PubMed1999

Weaver cerebellar granule neurons show altered expression of NMDA receptor subunits both in vivo and in vitro.

Biochemical, immunocytochemical, and molecular biological techniques were used to investigate the expression of N-methyl-D-aspartate (NMDA) receptor subunits in migration-deficient weaver mouse cerebellum in vivo and in primary cultures of the vermal weaver granule neurons with or without a rescue by verapamil. We found that both NMDAR1(zeta1) message and protein were expressed by the weaver granule neurons in situ. Immunocytochemical and biochemical analyses indicated that granule neurons of the weaver cerebellum expressed R1(zeta1) and R2A(epsilon1) subunits but showed little expression of the R2B(epsilon2) subunit. In weaver cerebellum, the R2B(epsilon2) subunit was primarily expressed in nerve fibers of the internal granule cell layer and white matter. Reverse-transcriptase-polymerase chain reaction followed by sequence analysis of the R1(zeta1) subunit indicated that the zeta1 subunit amplicons of both normal and weaver cerebella were identical, and that splice variants with exon 22 (1-2) and with or without exon 5 (a/b) or exon 21 (1-4) were detectable. The R2A(epsilon1), and R2B(epsilon2) subunits of the normal and weaver mouse cerebellum revealed no primary structural differences between the normal and weaver NMDA receptor subunits or the cloned mouse NMDA receptor subunits. In vermal cultures, normal granule neurons expressed all three NMDA receptor subunits (zeta1, epsilon1, and epsilon2), whereas the weaver neurons failed to express the epsilon2 subunit. Rescue of the weaver neurons by verapamil induced expression of the epsilon2 protein along the granule neuronal surfaces. The present results suggest that lack of the epsilon2 subunit in the weaver cerebellum may relate to the lack of functional NMDA receptors and/or to the migratory failure of the weaver granule neurons. Our data further suggest that NMDA receptor-mediated neurotoxicity is an unlikely mediator of neuronal death of the weaver granule neurons. In fact, down-regulation of the NMDA receptor expression and function may be a protective measure of the weaver granule neurons to reduce calcium entry via these receptors.

Animals↗
PubMed1999

Inhibition of isoniazid-induced hepatotoxicity in rabbits by pretreatment with an amidase inhibitor.

Isoniazid (INH), a widely used drug in the prophylaxis and treatment of tuberculosis, is associated with a 1 to 2% risk of severe and potentially fatal hepatotoxicity. There is evidence that the INH metabolite hydrazine plays an important role in the mechanism of this toxicity. Metabolism of INH leads to the production of hydrazine via both direct and indirect pathways. In both cases, the activity of an INH amidase is required to hydrolyze an amide bond. In the present study, using a model of INH-induced hepatotoxicity in rabbits, pretreatment of rabbits with the amidase inhibitor bis-p-nitrophenyl phosphate 30 min before injection of INH inhibited the formation of INH-derived hydrazine and decreased measures of hepatocellular damage, hepatic triglyceride accumulation, and hypertriglyceridemia. Bis-p-nitrophenyl phosphate also potently inhibited the production of hydrazine from INH in in vitro microsomal incubations (IC50 2 microM). Although hepatic glutathione stores are decreased, they are not depleted in animals with INH-induced hepatotoxicity. Significant effects on hepatic microsomal cytochrome P-450 1A1/2 and cytochrome P-450 2E1 activities suggest that these isozymes may be involved in the mechanism of the toxicity. In conclusion, this study demonstrates the importance of amidase activity in this rabbit model of hepatotoxicity and provides additional evidence in support of the role of hydrazine in the mechanism of INH-induced hepatotoxicity.

Amidohydrolases↗
PubMed1999

Neurotoxicity of isoniazid and its metabolites in cultures of mouse dorsal root ganglion neurons and hybrid neuronal cell line.

Isoniazid (INH) is one of the anti-tuberculosis drugs widely prescribed for patients since the early 1950s. It is relatively nontoxic but some patients develop peripheral neuropathy attributed to a disturbance of vitamin B6 metabolism. Some isoniazid metabolites are hepatotoxic but little is known about their neurotoxic property. Isoniazid and its metabolites including acetylisoniazid, acetylhydrazine, diacetylhydrazine, isonicotinic acid and hydrazine were examined for their potential neurotoxic effects in cultured mouse dorsal root ganglion (DRG) neurons and mouse neuroblastoma x DRG neuron hybrid cell line N18D3. Isoniazid did not cause neurotoxicity at exposures up to 7 days. Hydrazine was found to be the most toxic metabolite with LC50 values of 2.7 mM and 0.3 mM after 7 days of exposure in DRG neurons and N18D3 hybrid neurons, respectively. Other metabolites including acetylisoniazid, acetylhydrazine, diacetylhydrazine and isonicotinic acid had moderate to minor neurotoxic effects on N18D3 hybrid neurons. Pyridoxine, which is used in clinical practice to prevent or ameliorate the isoniazid-induced neuropathy, did not consistently reverse the neurotoxicity of any of the metabolites in the cell cultures, but some interaction with hydrazine cannot be ruled out. Pyridoxine itself was found to be neurotoxic both in DRG neurons and N18D3 hybrid neurons, in agreement with human peripheral sensory neuropathy caused by prolonged overdosage. The enzymes catalase and superoxide dismutase and the antioxidant agent selenium showed some protection against hydrazine neurotoxicity, suggesting an involvement of the generation of reactive oxygen species in the pathogenesis of isoniazid neuropathy. Both mouse DRG neurons and N18D3 mouse hybrid neurons were shown to be useful culture systems for elucidating the neurotoxicity mechanisms of agents causing sensory neuropathies and general neurotoxic effects in the nervous system.

Animals↗
PubMed1998

Influences of educational interventions and adverse news about calcium-channel blockers on first-line prescribing of antihypertensive drugs to elderly people in British Columbia.

BACKGROUND: The way in which dissemination of evidence changes medical practice needs to be better understood. Controversy about calcium-channel blockers (CCB) in the past 3 years has provided a natural experiment, enabling assessment of the impact of media stories, a national warning letter, a teleconference, small group workshops, and newsletters on first-line prescribing of antihypertensive drugs. METHODS: We included all physicians (4403) in British Columbia who prescribed a thiazide diuretic, beta-blocker, inhibitor of angiotensin-converting enzyme (ACE), or CCB as the first antihypertensive agent for 36,507 residents aged 66 years and over, with no previous or concurrent sign of underlying cardiovascular disease. We used a database covering all prescriptions to elderly people to measure the change in proportion of newly treated patients who received each class of drug as first-line therapy. We used a matched cohort design for assessment of the teleconference and workshops, a randomised community design for the newsletters, and time-series analysis for the media impacts. FINDINGS: The proportion of patients who received a CCB as first-line therapy declined gradually from 22% in early 1994 to 15% in late 1996. This proportion was not affected by two waves of adverse news about CCBs in 1995, but fell by 5% for 5 months and by 3% for 1 month after two waves in 1996. The proportion of patients who received either a CCB or an ACE inhibitor as first-line therapy, contrary to guidelines, was still 42% overall in 1996. The workshops and newsletters were followed by shifts from first-line CCB to first-line thiazide prescribing. INTERPRETATION: Changes in prescribing practices occur gradually with the accumulation of small impacts from educational interventions and lay media attention.

Adrenergic beta-Antagonists↗
PubMed1998

Birth weight and neonatal survival of harbour seal pups are positively correlated with genetic variation measured by microsatellites.

We examined the relations between fitness-related traits of wild harbour seal (Phoca vitulina) pups with microsatellite heterozygosity, and with a measure of genomic diversity based on the mean squared distance between microsatellite alleles within an individual, mean d2. Birth weight was positively influenced by maternal age, pup sex, and either mean d2 or individual heterozygosity in separate multiple regression models. The association of birth weight with mean d2 was stronger than that with heterozygosity, however. The factors maternal age, pup sex, and mean d2 combined to account for 36.8% of the variation in birth weight, with mean d2 accounting for the greatest explanatory power (52.3% of the variance explained). Pups which survived until weaning had significantly higher mean d2 than pups which died, independent of birth weight. These effects are consistent with heterosis resulting from recent population mixing, and/or inbreeding depression in this population. Mean d2 thus provides (i) a better measure of individual genetic variability than heterozygosity for microsatellite data; and (ii) a convenient tool for assessing the effects of inbreeding and outbreeding in natural populations.

Animals↗
PubMed1998

Distinct functional stoichiometry of potassium channel beta subunits.

Shaker-type potassium channels play important roles in determining the electrical excitability of cells. The native channel complex is thought to be formed by four pore-forming alpha subunits that provide four interaction sites for auxiliary modulatory Kvbeta subunits. Because Kvbeta subunits possess diverse modulatory activities including either up-regulation or down-regulation of potassium currents, differential assembly of the alpha-beta complex could give rise to diverse current properties. However, the detailed physical and functional stoichiometry of the alpha-beta complex remains unknown. Kvbeta1 subunits reduce potassium currents through inactivation, whereas Kvbeta2 subunits enhance potassium currents by inhibiting the Kvbeta1-mediated inactivation and at the same time by promoting the surface expression of certain potassium channels. In this report we show that Kvbeta1 and Kvbeta2 of the Shaker-type potassium channels display distinct functional stoichiometry to interact with the Kv1 alpha subunits, a subfamily of Shaker-type potassium channels. The interaction of Kvbeta1 subunits with alpha subunits is consistent with the alpha4betan model, where n equals 0, 1, 2, 3, or 4, depending upon the relative concentration of alpha and beta subunits. The alpha4betan stoichiometry allows for gradual changes of the Kvbeta1-mediated inactivation. In contrast, Kvbeta2 subunits self-associate to form oligomers and interact with the alpha subunits via alpha4beta4 stoichiometry, which permits effective multivalent associations with alpha subunits. Such distinct functional stoichiometry of Kvbeta1 and Kvbeta2 provides a molecular mechanism that is well suited to their contrasting activities of up-regulation or down-regulation of potassium currents.

Animals↗