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Biomedical subjects

D Walton

Publications and source records attributed to D Walton.

At least 19 recordsLinked to original sources
PubMed2005

Use of the Diversi Lab System for species and strain differentiation of Fusarium species isolates.

Advances in molecular typing of fusariosis would facilitate the study of its epidemiology. We tested 26 such isolates by the commercially available Diversi Lab System. The system utilizes automated repetitive sequence-based PCR (rep-PCR) and web-based data analyses. rep-PCR dendrogram cluster analysis showed agreement with species sequence identification (elongation factor 1 alpha gene). Additionally, subtype differences within the same species were noted.

Bacterial Typing Techniques↗
PubMed2004

Identification to the species level and differentiation between strains of Aspergillus clinical isolates by automated repetitive-sequence-based PCR.

A commercially available repetitive-sequence-based PCR (rep-PCR) DNA fingerprinting assay adapted to an automated format, the DiversiLab system, enables rapid microbial identification and strain typing. We explored the performance of the DiversiLab system as a molecular typing tool for 69 Aspergillus isolates (38 A. fumigatus, 15 A. flavus, and 16 A. terreus isolates) had been previously characterized by morphological analysis. Initially, 27 Aspergillus isolates (10 A. fumigatus, 9 A. flavus, and 8 A. terreus isolates) were used as controls to create a rep-PCR-based DNA fingerprint library with the DiversiLab software. Then, 42 blinded Aspergillus isolates were typed using the system. The rep-PCR-based profile revealed 98% concordance with morphology-based identification. rep-PCR-based DNA fingerprints were reproducible and were consistent for DNA from both hyphae and conidia. DiversiLab dendrogram reports correctly identified all A. fumigatus (n = 28), A. terreus (n = 8), and A. flavus (n = 6) isolates in the 42 blinded Aspergillus isolates. rep-PCR-based identification of all isolates was 100% in agreement with the contiguous internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) sequence-based identification of the respective isolates. Additionally, the DiversiLab system could demonstrate strain-level differentiation of A. flavus and A. terreus. Automated rep-PCR may be a time-efficient, effective, easy-to-use, novel genotyping tool for identifying and determining the strain relatedness of fungi. This system may be useful for epidemiological studies, molecular typing, and surveillance of Aspergillus species.

Aspergillus↗
PubMed2001

A spectrum of FOXC1 mutations suggests gene dosage as a mechanism for developmental defects of the anterior chamber of the eye.

Mutations in the forkhead transcription-factor gene (FOXC1), have been shown to cause defects of the anterior chamber of the eye that are associated with developmental forms of glaucoma. Discovery of these mutations was greatly facilitated by the cloning and characterization of the 6p25 breakpoint in a patient with both congenital glaucoma and a balanced-translocation event involving chromosomes 6 and 13. Here we describe the identification of novel mutations in the FOXC1 gene in patients with anterior-chamber defects of the eye. We have detected nine new mutations (eight of which are novel) in the FOXC1 gene in patients with anterior-chamber eye defects. Of these mutations, five frameshift mutations predict loss of the forkhead domain, as a result of premature termination of translation. Of particular interest is the fact that two families have a duplication of 6p25, involving the FOXC1 gene. These data suggest that both FOXC1 haploinsufficiency and increased gene dosage can cause anterior-chamber defects of the eye.

Anterior Chamber↗
PubMed2001

Drivers' biased perceptions of speed and safety campaign messages.

One hundred and thirteen drivers were surveyed for their perceptions of driving speed to compare self-reported average speed, perceived average-other speed and the actual average speed, in two conditions (50 and 100 kph zones). These contrasts were used to evaluate whether public safety messages concerning speeding effectively reach their target audience. Evidence is presented supporting the hypothesis that drivers who have a biased perception of their own speed relative to others are more likely to ignore advertising campaigns encouraging people not to speed. A method of self-other-actual comparisons detects biased perceptions when the standard method of self-other comparison does not. In particular, drivers exaggerate the perceived speed of others and this fact is masked using traditional methods. The method of manipulation is proposed as a way to evaluate the effect of future advertising campaigns, and a strategy for such campaigns is proposed based on the results of the self-other comparisons.

Adult↗
PubMed2000

Molecular basis of a progressive juvenile-onset hereditary cataract.

In a recent paper, patients with a progressive juvenile-onset hereditary cataract have been reported to have a point mutation in the human gammaD crystallin gene (Stephan, D. A., Gillanders, E., Vanderveen, D., Freas-Lutz, D., Wistow, G., Baxevanis, A. D., Robbins, C. M., VanAuken, A., Quesenberry, M. I., Bailey-Wilson, J., et al. (1999) Proc. Natl. Acad. Sci. USA 96, 1008-1012). This mutation results in the substitution of Arg-14 in the native protein by a Cys residue. It is not understood how this mutation leads to cataract. We have expressed recombinant wild-type human gammaD crystallin (HGD) and its Arg-14 to Cys mutant (R14C) in Escherichia coli and show that R14C forms disulfide-linked oligomers, which markedly raise the phase separation temperature of the protein solution. Eventually, R14C precipitates. In contrast, HGD slowly forms only disulfide-linked dimers and no oligomers. These data strongly suggest that the observed cataract is triggered by the thiol-mediated aggregation of R14C. The aggregation profiles of HGD and R14C are consistent with our homology modeling studies that reveal that R14C contains two exposed cysteine residues, whereas HGD has only one. Our CD, fluorescence, and differential scanning calorimetric studies show that HGD and R14C have nearly identical secondary and tertiary structures and stabilities. Thus, contrary to current views, unfolding or destabilization of the protein is not necessary for cataractogenesis.

Adolescent↗
PubMed1999

Effects of providing hospital-based doulas in health maintenance organization hospitals.

OBJECTIVE: To evaluate whether providing doulas during hospital-based labor affects mode of delivery, epidural use, breast-feeding, and postpartum perceptions of the birth, self-esteem, and depression. METHODS: This was a randomized study of nullipara enrollees in a group-model health maintenance organization who delivered in one of three health maintenance organization-managed hospitals; 149 had doulas, and 165 had usual care. Study data were obtained from the mothers' medical charts, study intake forms, and phone interviews conducted 4-6 weeks postpartum. RESULTS: Women who had doulas had significantly less epidural use (54.4% versus 66.1%, P < .05) than women in the usual-care group. They also were significantly (P < .05) more likely to rate the birth experience as good (82.5% versus 67.4%), to feel they coped very well with labor (46.8% versus 28.3%), and to feel labor had a very positive effect on their feelings as women (58.0% versus 43.7%) and perception of their bodies' strength and performance (58.0% versus 41.0%). The two groups did not differ significantly in rates of cesarean, vaginal, forceps, or vacuum delivery, oxytocin administration; or breast-feeding, nor did they differ on the postpartum depression or self-esteem measures. CONCLUSION: For this population and setting, labor support from doulas had a desirable effect on epidural use and women's perceptions of birth, but did not alter need for operative deliveries.

Adolescent↗
PubMed1998

An exploration of the perceptions of the average driver's speed compared to perceived driver safety and driving skill.

This study investigates the self-enhancement bias in driver attitudes, the finding that drivers rate themselves better than the average driver on safety and skill perceptions (Svenson, 1978, 1981; McCormick et al., 1986). A sample of 86 New Zealand drivers were asked their perceptions of their own and others' speeds in two conditions, 50 km/h and 100 km/h. The results established the self-enhancement bias for speed and safety, but not skill. Between 85% and 90% of drivers claimed to drive slower than the 'average driver.' A new methodological technique derived from Harré and Gillett (1994) was used to investigate the direction of the self-enhancement bias. The results support the Downward Comparison Theory (Wills, 1981) because drivers consider other drivers negatively, rather than exaggerating their self-perceptions.

Acceleration↗
PubMed1998

Manipulation for cervical spinal dislocation under general anaesthesia: serial review for 4 years.

Manipulation under anaesthesia is an important method to reduce cervical spinal dislocations in the acute stage. Causes of failure have not been clearly identified and neurological complications can be the major concern. All cervical dislocations have been traditionally treated by manipulation under anaesthesia in the Christchurch Spinal Injuries Unit as the primary treatment. We reviewed all 31 patients treated from 1991-1995, with detailed documentation of neurological progression and final outcome. Three patterns were identified: bilateral dislocation, unifacet dislocation and fracture dislocation. Most of the dislocations (74%) were successfully reduced by manipulation alone with minimum complications. The remaining 26% patients required open reduction. The predominant causes of failure of reduction by manipulation were co-existing fractures. The success rate of reduction by manipulation was 90% for pure bifacet and unifacet dislocations, but was only 22% for the fracture dislocations. The study concluded that manipulation under anaesthesia is a safe and effective procedure for pure cervical spinal dislocations. Fractures related to the dislocation should be identified early and open reduction be considered.

Adolescent↗
PubMed1998

Results of peripheral laser photocoagulation in pars planitis.

PURPOSE: To determine the effect of peripheral retinal laser photocoagulation (PLP) on visual acuity, intraocular inflammation, and other ocular findings, including retinal neovascularization in eyes with pars planitis. METHODS: A retrospective chart review of eyes with pars planitis that had undergone PLP. RESULTS: Twenty-two eyes in 17 patients with pars planitis had undergone treatment with PLP at 2 centers. The mean age at the time of treatment was 19.3 years. Following treatment, mean follow-up was 16.3 months (range, 6 to 37 months). Mean visual acuity was 20/60 preoperatively and 20/50 postoperatively. This level of improvement was not statistically significant (P > .10), but there was a statistically significant decrease in the use of corticosteroids between the preoperative examination and the last postoperative examination (86% versus 27%, P < .05). There was also a statistically significant decrease in vitritis at the last follow-up (P = .0008) and a decrease in neovascularization of the vitreous base (P = .03) and in clinically apparent cystoid macular edema (P = .02). Epiretinal membranes were noted in 23% of eyes preoperatively and in 45% of eyes postoperatively. Only one of these epiretinal membranes was considered to be visually significant. One eye developed a tonic dilated pupil, which slowly improved. CONCLUSIONS: Although the long-term natural history of clinical findings in pars planitis is not well documented, PLP appears to decrease the need for corticosteroids while stabilizing visual acuity. It also appears to decrease vitreous inflammation. PLP has few complications and should be considered in patients with pars planitis who are unresponsive or have adverse reactions to corticosteroids.

Adolescent↗
PubMed1998

Surveillance of leptospiral carriage by feral rats in Barbados.

Rodents, particularly rats, are widely held to be the source of most human cases of leptospirosis. Feral rats were trapped at sites throughout Barbados during two six month surveys: from October to March 1986/87 and from October to March 1994/95. During the first survey, 63 rats were trapped, of which 26 (41%) were identified as Rattus rattus and 37 (59%) as Rattus norvegicus. In the second study, 100 rats were trapped, of which R. rattus comprised 24% (24) and R. norvegicus 76% (76). Cultures of blood, urine and kidney were made in EMJH medium. Leptospires were isolated from 12/63 (19%) and from 16/100 (16%) of the rats during 1986/87 and 1994/95, respectively; 27/28 isolates were recovered from the kidneys or urine or both, while only one isolate was recovered from the blood. During the first study, isolates were identified as serovars copenhageni (11) and arborea (1), while in the second study, serovars copenhageni (9), arborea (5) and bim (1) were identified; one isolate was lost before it could be identified. In the first study, antibodies were detected by microscopic agglutination at a titre of > or = 100 in 26/62 (42%) of rats tested, while in the second survey, 5/100 (5%) of rats had similar titres. In two surveys, conducted eight years apart, we confirmed that rats in Barbados are commonly infected with leptospires, and that viable organisms are found in the kidneys and urine, evidence of chronic infection and thus excretion of leptospires in rodent urine. Moreover, the predominant serovar isolated was copenhageni, of which Rattus spp. are the worldwide reservoir. There was little evidence that rats act as a reservoir for the serovar bim, the most common cause of human leptospirosis in Barbados.

Animals↗
PubMed1997

Spurious hypophosphatemia in a patient with multiple myeloma.

We report a patient with multiple myeloma and a prolonged history of hypophosphatemia who had remained asymptomatic. Extensive evaluation for a cause, including the search for a renal tubular disorder, oncogenous osteomalacia, or a parathyroid hormone (PTH)-related protein was unproductive. Renal biopsy showed no evidence of myeloma kidney. Subsequent mixing of the immunoglobulin G (IgG) fraction from the patient's serum with normal human serum, confirmed that the observed hypophosphatemia was spurious, resulting from interference of large amounts of an abnormal IgG with a standard automated laboratory assay for phosphate.

Autoanalysis↗
PubMed1995

Patient with craniosynostosis and marfanoid phenotype (Shprintzen-Goldberg syndrome) and cloverleaf skull.

Marfanoid phenotype with craniosynostosis (Shprintzen-Goldberg syndrome) is a rare disorder previously described in only 5 patients. We report on the sixth known patient with this condition. The findings which distinguish our patient from others reported previously are that she was ascertained prenatally as having a cloverleaf skull; this is the first female patient described with this condition. Postnatally, she presented with arachnodactyly, camptodactyly, and clover-leaf skull. Imaging studies of the brain documented microcephaly with malformed brain, hydrocephaly, and hypoplasia of the corpus callosum. She also had choanal atresia and stenosis, a clinical finding previously reported only once, in this disorder.

Abnormalities, Multiple↗