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Biomedical subjects

L Turner

Publications and source records attributed to L Turner.

At least 109 records · Page 6Linked to original sources
PubMed1994

Unilateral retinoblastoma: new intraocular tumours after treatment.

A retrospective chart review of 427 eyes diagnosed with unilateral retinoblastoma was performed to determine which eyes, which patients, and when new intraocular tumours would develop after treatment. Mean follow up was 8.16 years. Twenty five (6%) of 427 unilateral retinoblastoma patients developed new intraocular tumours after treatment. Five (1%) unilateral patients who were previously treated with enucleation developed new tumours (in the fellow eye). Fifteen (24%) unilateral patients who were previously treated with external beam radiation developed new tumours (equally in either eye). New tumours did not develop in the macula of either eye. The relative risk of developing new intraocular tumours after treatment was 16% in patients diagnosed before 1 year old and 2.2% for patients diagnosed after 1 year old (p < 0.001). The mean time to onset for the development of new tumours after treatment was 0.74 years; no new tumours appeared after 7.5 years of age. Those patients who are diagnosed with unilateral retinoblastoma in the first 6 months of life and have a family history of the disease are at greatest risk of developing new intraocular tumours.

Age Factors↗
PubMed1994

Validation of a new instrument for determining migraine prevalence: the UCSD Migraine Questionnaire.

To provide a reliable instrument for use in large population surveys, we developed a short questionnaire based on existing International Headache Society diagnostic criteria and administered the questionnaire to 50 consecutive patients seeking evaluation at a university-based headache clinic. A single neurologist subsequently examined all patients. Based only on the questionnaires, reviewers scored each patient as having migraine with aura, migraine without aura, or nonmigrainous headache. High predictive validity and low interobserver variability between the examining neurologist and the independent reviewers suggest that the questionnaire may be quite useful as a survey instrument.

Adolescent↗
PubMed1993

Illness after measles-mumps-rubella vaccination.

OBJECTIVES: To provide accurate information on the common sequelae of measles-mumps-rubella (MMR) vaccination and to compare post-vaccine symptoms in children vaccinated at 13 and 15 months. DESIGN: Prospective cluster randomized controlled trial. SETTING: Twenty-two family practices in southwestern Ontario. PATIENTS: All 376 infants who were due to receive MMR vaccine in the next year, 253 (67.3%) successfully completed the study. INTERVENTION: MMR vaccine administered at 13 months by half of the family physicians and at 15 months by the remaining half. OUTCOME MEASURES: Family physician's physical findings in children 7 days and 30 days after vaccine; reported illnesses by mothers in a daily diary in the month before and after vaccination and medical records of visits to family physicians and hospital admissions in the month before and after vaccination. RESULTS: Compared with the incidence rates in the corresponding weeks before vaccination, the rates of lymphadenopathy (23.8%) and fever (16.8%) were higher 1 week afterward and the rate of rash (26.9%) was higher 7 to 14 days afterward. Fewer health problems were reported in the third and fourth weeks after vaccination than in the corresponding weeks beforehand. Hospital admissions after vaccination were no more frequent than those before once cause and time of admission were taken into account. The two age groups did not differ in any of the outcomes. CONCLUSIONS: Mothers should be informed about the possibility of increased physical findings in the weeks after MMR vaccination, especially lymphadenopathy, nasal discharge and rash. Since the occurrence of sequelae does not seem to differ significantly between 13-month-old recipients and 15-month-old recipients, it should not influence the decision of when to administer the vaccine.

Age Factors↗
PubMed1993

A defective visual pathway in children with reading disability.

BACKGROUND: The possibility that reading disability in children is associated with visual problems is in dispute. We sought to test the existence of this association by using electrophysiologic techniques to measure the processing of visual information in the magnicellular and parvicellular visual pathways of the brain. METHODS: Visual evoked potentials were measured with scalp electrodes in children 8 to 11 years old who were normal readers and in those with reading disability. The potentials were measured for targets with low (0.5 cycle per degree of visual angle) and high (4.5 cycles per degree) spatial frequency, surrounded by either a steady background or a uniform-field flickering 12 times per second. A flickering field normally reduces the amplitude and increases the latency of a transient potential evoked by a low-spatial-frequency target, which preferentially excites the magnicellular visual pathway, but has little effect on the response to a high-spatial-frequency target. RESULTS: With a steady background, the latencies of the early components (N1 and P1) of the visual evoked potentials were longer in the reading-disabled children than in the normal readers when the low-spatial-frequency target was used, but not when the high-spatial-frequency target was used. In normal readers, the flickering background increased the latency and reduced the amplitude of the early components, whereas in the reading-disabled children only the amplitude was affected. No differences were observed in either group with the high-spatial-frequency target. CONCLUSIONS: The pattern of results suggests that the response of the magnicellular visual pathway is slowed in reading-disabled children, who do not, however, have a general slowing of the visual response. The possibility that there is a cause-and-effect relation between these findings and reading disability will require further study.

Child↗
PubMed1993

Genetic aspects of the organization of legumin genes in pea.

We have compared physical and genetic maps of the region around the legJ gene in pea. In this vicinity there are four B-type legumin genes, arranged as two close pairs. The detection of a recombination event within this gene cluster allows the orientation of this group of genes within the surrounding linkage group to be determined. The relationship between physical and genetic distances in this region is discussed, as are the implications of this for relating physical and genetic maps elsewhere in the pea genome.

Alleles↗
PubMed1993

Repeated sequences as genetic markers in pooled tissue samples.

We show, using the PDR1 element of pea, that dispersed repeated sequences of moderate copy number can be used simply and efficiently to generate markers linked to a trait of interest. Inspection of hybridization patterns of repeated sequences to DNA mixtures of pooled genotypes is a sensitive way of detecting such markers. The large number of bands in tracks of digests of these mixtures allows the simultaneous sampling of loci at many places in the genome, and the many unlinked loci serve as internal controls. It is also shown that intensity ratios calculated from these band differences can be used to give a rough estimate of linkage distance.

Chromosome Mapping↗
PubMed1993

Torque generated by the flagellar motor of Escherichia coli.

Cells of the bacterium Escherichia coli were tethered and spun in a high-frequency rotating electric field at a series of discrete field strengths. This was done first at low field strengths, then at field strengths generating speeds high enough to disrupt motor function, and finally at low field strengths. Comparison of the initial and final speed versus applied-torque plots yielded relative motor torque. For backward rotation, motor torque rose steeply at speeds close to zero, peaking, on average, at about 2.2 times the stall torque. For forward rotation, motor torque remained approximately constant up to speeds of about 60% of the zero-torque speed. Then the torque dropped linearly with speed, crossed zero, and reached a minimum, on average, at about -1.7 times the stall torque. The zero-torque speed increased with temperature (about 90 Hz at 11 degrees C, 140 Hz at 16 degrees C, and 290 Hz at 23 degrees C), while other parameters remained approximately constant. Sometimes the motor slipped at either extreme (delivered constant torque over a range of speeds), but eventually it broke. Similar results were obtained whether motors broke catastrophically (suddenly and completely) or progressively or were de-energized by brief treatment with an uncoupler. These results are consistent with a tightly coupled ratchet mechanism, provided that elastic deformation of force-generating elements is limited by a stop and that mechanical components yield at high applied torques.

Biomechanical Phenomena↗
PubMed1993

A link between adenosine, ATP-sensitive K+ channels, potassium and muscle vasodilatation in the rat in systemic hypoxia.

1. In anaesthetized rats, systemic hypoxia evoked hyperventilation, tachycardia, a fall in arterial pressure, vasodilatation in skeletal muscle and increases in K+ concentration measured in arterial plasma ([K+]a), venous efflux from muscle ([K+]v) and in right atrial plasma ([K+]at). The ATP-sensitive potassium (K+ATP) channel inhibitor glibenclamide (10 or 20 mg kg-1 i.v.) reduced the muscle vasodilatation and increase in [K+]v, but had no significant effect on the other changes. 2. The adenosine receptor antagonist, 8-phenyltheophylline (8-PT, 10 mg kg-1 i.v.) had similar effects to glibenclamide. 3. Glibenclamide reduced the muscle vasodilatation evoked by the adenosine analogue, 2-chloroadenosine given i.v. (30 micrograms kg-1). 4. Infusion of adenosine (0.3 mg kg-1 min-1 for 5 min) into the hindlimb evoked muscle vasodilatation and an increase in [K+]v, both of which were abolished by 8-PT. 5. We propose that during systemic hypoxia, part of the muscle vasodilatation that can be attributed to adenosine is due to the action of K+, which is released from skeletal muscle fibres through glibenclamide-sensitive K+ channels (possibly K+ATP channels) that are activated by adenosine. This may be a general mechanism for the vasodilator influence of adenosine.

2-Chloroadenosine↗