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Biomedical subjects

D Vickers

Publications and source records attributed to D Vickers.

At least 19 recordsLinked to original sources
PubMed2003

Familial growth and skeletal features associated with SHOX haploinsufficiency.

This study was designed to determine the intrafamilial effect of SHOX haploinsufficiency on stature, by comparing the growth and phenotype of 26 SHOX haploinsufficient individuals with 45 relatives and population standards. It confirmed that SHOX haploinsufficiency leads to growth restriction from birth to final height. Compared to unaffected siblings, the SHOX haploinsufficient cohort was 2.14 SDS (3.8 cm) shorter at birth and 2.1 SDS shorter through childhood. At final height females were 2.4 SDS (14.4 cm) shorter and males 0.8 SDS (5.3 cm) shorter than normal siblings. The family height analysis suggests that the effect of SHOX haploinsufficiency on growth may have been previously underestimated at birth and overestimated in males at final height. SHOX haploinsufficiency leads to short arms in 92%, bilateral Madelung deformity in 73% and short stature in 54%. Females were more severely affected than males. We conclude that SHOX is a major growth gene and that mutations are associated with a broad range of phenotype.

Adolescent↗
PubMed2003

Effect of 24 months of recombinant growth hormone on height and body proportions in SHOX haploinsufficiency.

Leri-Weill syndrome (LWS) is a skeletal dysplasia with mesomelic short stature, bilateral Madelung deformity (BMD) and SHOX (short stature homeobox-containing gene) haploinsufficiency. The effect of 24 months of recombinant human growth hormone (rhGH) therapy on the stature and BMD of two females with SHOX haploinsufficiency (demonstrated by fluorescence in situ hybridisation) and LWS was evaluated. Both patients demonstrated an increase in height standard deviation score (SDS) and height velocity SDS over the 24 months of therapy. Patient 1 demonstrated a relative increase in arm-span and upper segment measurements with rhGH while patient 2 demonstrated a relative increase in lower limb length. There was appropriate advancement of bone age, no adverse events and no significant deterioration in BMD. In this study, 24 months of rhGH was a safe and effective therapy for the disproportionate short stature of SHOX haploinsufficiency, with no clinical deterioration of BMD.

Adolescent↗
PubMed2001

Human performance on visually presented Traveling Salesman problems.

Little research has been carried out on human performance in optimization problems, such as the Traveling Salesman problem (TSP). Studies by Polivanova (1974, Voprosy Psikhologii, 4, 41-51) and by MacGregor and Ormerod (1996, Perception & Psychophysics, 58, 527-539) suggest that: (1) the complexity of solutions to visually presented TSPs depends on the number of points on the convex hull; and (2) the perception of optimal structure is an innate tendency of the visual system, not subject to individual differences. Results are reported from two experiments. In the first, measures of the total length and completion speed of pathways, and a measure of path uncertainty were compared with optimal solutions produced by an elastic net algorithm and by several heuristic methods. Performance was also compared under instructions to draw the shortest or the most attractive pathway. In the second, various measures of performance were compared with scores on Raven's advanced progressive matrices (APM). The number of points on the convex hull did not determine the relative optimality of solutions, although both this factor and the total number of points influenced solution speed and path uncertainty. Subjects' solutions showed appreciable individual differences, which had a strong correlation with APM scores. The relation between perceptual organization and the process of solving visually presented TSPs is briefly discussed, as is the potential of optimization for providing a conceptual framework for the study of intelligence.

Attention↗
PubMed2001

Decision making and memory: a critique of Juslin and Olsson's (1997) sampling model of sensory discrimination.

P. Juslin and H. Olsson's (1997) distinction between Thurstonian and Brunswikian uncertainty is examined and their sampling model of sensory discrimination analyzed as a representative of the class of memoryless decision processes. The separate characteristics and combined behavior of 4 main components of the model are explored: (a) the basic decision process, (b) the assumption of deadline responding, (c) the moving window model of memory, and (d) the hypothesized basis for confidence. It is argued that grafting a moving window memory onto a memoryless decision process has several undesirable consequences. Moreover, the suggested basis for confidence leads to predictions that are counterintuitive and unsupported by empirical evidence. It is concluded that the window-sampling model is a maladapted combination of inappropriate elements, which is implausible as a model of decision making, memory, or confidence, in sensory discrimination.

Decision Making↗
PubMed2001

Histopathological analysis of Leri-Weill dyschondrosteosis: disordered growth plate.

Leri-Weill syndrome (LWS) is a dominant (pseudoautosomal) skeletal dysplasia with mesomelic short stature and bilateral Madelung deformity, due to dyschondrosteosis of the distal radius. It results from the loss of one copy of the Short Stature Homeobox Gene (SHOX) from the tip of the short arm of the X or Y chromosome. SHOX molecular testing enabled us to evaluate the histopathology of the radial physis in LWS patients with a documented SHOX abnormality. A widespread disorganisation of physeal anatomy was revealed with disruption of the normal parallel columnar arrangement of chondrocytes. Tandem stacking of maturing chondrocytes within columns was replaced by a side-by-side arrangement. The presence of hypertrophic osteoid with micro-enchondromata in the radial metaphysis suggests abnormal endochondral ossification. The Vickers' ligament was confirmed to blend with the triangular fibrocartilage complex (TFCC). This histopathological study demonstrates that the zone of dyschondrosteosis in LWS is characterised by marked disruption of normal physeal chondrocyte processes and that a generalised physeal abnormality is present.

Adolescent↗
PubMed2000

The importance of the convex hull for human performance on the traveling salesman problem: a comment on MacGregor and Ormerod (1996)

MacGregor and Ormerod (1996) have presented results purporting to show that human performance on visually presented traveling salesman problems, as indexed by a measure of response uncertainty, is strongly determined by the number of points in the stimulus array falling inside the convex hull, as distinct from the total number of points. It is argued that this conclusion is artifactually determined by their constrained procedure for stimulus construction, and, even if true, would be limited to arrays with fewer than around 50 points.

Humans↗
PubMed1999

Prospective, randomized trial comparing four biofeedback techniques for patients with constipation.

PURPOSE: The aim of this study was to compare four methods of biofeedback for patients with constipation. METHODS: Thirty-six patients were prospectively, randomly assigned to one of four protocols: 1) outpatient intra-anal electromyographic biofeedback training; 2) electromyographic biofeedback training plus intrarectal balloon training; 3) electromyographic biofeedback training plus home training; or 4) electromyographic biofeedback training, balloon training, and home training. All 36 patients received weekly one-hour outpatient biofeedback training. Success was measured by increased unassisted bowel movements and reduction in cathartic use. In all instances patients maintained a daily log in which documentation was maintained regarding each bowel evacuation and the need for any cathartics. RESULTS; There was a statistically significant increase in unassisted bowel movements for Groups 1, 2, and 4 (P < 0.05) and a reduction in the use of cathartics in Groups 1, 2, and 3 (P < 0.05). CONCLUSION: There was a significant improvement in outcome after all four treatment protocols for constipation; however, no significant difference was found among the treatments. Therefore, electromyographic biofeedback training alone is as effective as with the addition of balloon training, home training, or both.

Adolescent↗
PubMed1997

Biofeedback for intractable rectal pain: outcome and predictors of success.

PURPOSE: A number of modalities have been used for the treatment of intractable rectal pain, with varying degrees of success. Electromyography (EMG)-based biofeedback therapy has been used in the treatment of this condition during the past six years. MATERIALS AND METHODS: Medical records of 86 patients who completed at least one session of biofeedback for rectal pain between February 1989 and August 1995 were retrospectively reviewed. All sessions were one-hour outpatient encounters with a trained biofeedback therapist. There were 31 male and 55 female patients with a median age of 68 (range, 12-96) years. Surgery (19.8 percent) or stress (15.1 percent) were frequently cited as precipitating factors for the development of rectal pain. Eleven patients completed only one session of biofeedback and were excluded from further analysis. Of the remaining patients, 28 complained of concomitant constipation. Assessment of the benefit of therapy was based on the patients' subjective reports of the level of symptoms, aided by a linear analog scale. RESULTS: Twenty six patients (34.7 percent) reported an improvement in symptoms. Outcome was not influenced by patients' ages (P = 0.63), duration of symptoms (P = 1.0), or a prior history of surgery (P = 0.14). Alleviation of symptoms was not significantly related to the presence of paradoxical puborectalis contraction demonstrated on either EMG (P = 1) or defecography (P = 0.12). Importantly, outcome was significantly improved in patients who completed the treatment schedule compared with those who self-discharged (P < 0.001). CONCLUSIONS: Although idiopathic rectal pain is difficult to treat, EMG-based biofeedback can produce alleviation of symptoms. However, success depends on patients' willingness to pursue a full course of therapy.

Aged↗
PubMed1997

Memory capacity and intelligence: novel techniques for evaluating rival models of a fundamental information-processing mechanism.

Data from a fundamental cognitive task in which participants discriminate the relative frequency of visual or auditory binary stimuli were examined. Accuracy on this task correlates well with psychometric intelligence. The experimental paradigm is highly tractable, lending itself to rigorous analyses of precisely defined simulation models. Numerous models are evaluated, using multiple comparisons between response patterns of individual (and pooled) participants and predictive measures based on simulations for each trial sequence. Implications for theoretical accounts of short-term memory, discrimination, and absolute judgement as well as the measurement of individual differences in cognitive ability, are discussed. The results suggest a reinterpretation of memory capacity and support a new kind of model (with a single estimable parameter) in which discrete, valued units of information are stochastically displaced by further input.

Acoustic Stimulation↗
PubMed1997

Outcome and predictors of success of biofeedback for constipation.

BACKGROUND: A study was undertaken to determine outcome and to identify predictors of success for biofeedback for constipation. METHODS: Patients who had at least one biofeedback session were evaluated whether or not they completed a treatment course. Parameters assessed included use of cathartics, number of spontaneous bowel movements per week, presence of rectal pain, number of biofeedback sessions and results of anorectal physiology. RESULTS: A total of 194 patients (59 male, 135 female) of median age 71 (range 11-96) years, including 30 with concomitant rectal pain, were treated. The median number of spontaneous bowel movements per week before treatment was 0. Some 35 per cent of patients had complete success (three or more spontaneous bowel movements per week with discontinuation of cathartics), 13 per cent had partial success (fewer than three spontaneous bowel movements per week with continued use of cathartics) and 51 per cent had no improvement. Neither patient age, sex nor duration of symptoms significantly affected outcome. Only 18 per cent of patients who had between two and four sessions had complete success, compared with 44 per cent of those who had five or more (P < 0.001). A total of 63 per cent of patients who completed the treatment protocol experienced complete success, compared with 25 per cent of those who self-discharged (P < 0.0001). CONCLUSIONS: This large study indicates that the success rate of biofeedback for patients with constipation is less than previously reported. However, the success rate improves significantly after five or more sessions and is significantly related to the patient's willingness to complete treatment.

Adolescent↗
PubMed1996

The geometric structure, construction, and interpretation of path-following (trail-making) tests.

Diagnostic comparisons of performance on parts A and B of the Trail Making Test (TMT) assume that path structure in the two parts is equivalent but that task complexity is greater for B. The two parts are shown to differ with respect to length and angular variability. However, measures of fractal dimension show no difference in structural complexity between paths A and B. This analysis suggests a principled method for generating alternative pathways, varying in complexity, and opens the way for a systematic study of path-following. It also suggests that path-following may be interpretable within a general approach, in which perceptual, linguistic, reasoning and motor processes are seen as related through different groups of geometric transformations.

Adult↗
PubMed1992

Madelung deformity: surgical prophylaxis (physiolysis) during the late growth period by resection of the dyschondrosteosis lesion.

The majority of cases of Madelung deformity are caused by hereditary dyschondrosteosis at the wrist. The principal lesion in the ulnar zone of the distal radial physis retards growth asymmetrically, especially in late childhood. Resection of this zone and its replacement with autologous fat (Langenskiöld procedure, or physiolysis) restores growth and minimizes deformity. The resection of an abnormal ligament tethering the lunate proximally may assist carpal advancement. A series of 17 patients (24 wrists) treated over a 12-year period is presented, with sufficient follow-up for evaluation of 11 patients (15 wrists). The results of this prophylactic procedure are encouraging, and, if it is performed early, the authors believe that Madelung deformity may be preventable, or at least controllable.

Adipose Tissue↗
PubMed1992

Intra-operative patient-controlled sedation. Comparison of patient-controlled propofol with patient-controlled midazolam.

Propofol and midazolam were compared for intra-operative patient-controlled sedation in 40 ASA 1 day patients undergoing surgical extraction of third molar teeth under local anaesthesia. All patients initially received 0.7 micrograms.kg-1 fentanyl. Patients in the propofol group self-administered 20 mg (2 ml over 6 s) bolus doses of propofol; successful demands averaged 8.0 (SD 4.4) and unsuccessful demands (during the 1 min lockout period) 2.8 (SD 4.1). The midazolam group self-administered 0.5 mg (2 ml over 6 s) bolus doses and averaged 14.0 (SD 6.3) and 17.6 (SD 19.8) successful and unsuccessful demands respectively. Postoperative memory, measured with delayed free recall, and postoperative mental performance, measured with the frequency accrual speed test index, were both significantly less impaired in the propofol group. Although there was no significant difference in patient satisfaction, measured postoperatively, propofol was judged the more suitable agent for patient-controlled sedation, because of its more rapid response to fluctuating intra-operative requirements, superior recovery characteristics and beneficial effect on mood.

Adult↗
PubMed1992

Double-blind comparison of patient recovery after induction with propofol or thiopentone for day-case relaxant general anaesthesia.

Postoperative recovery after induction with either propofol or thiopentone has been compared in forty ASA I unpremedicated day surgery patients undergoing surgical extraction of third molar teeth under relaxant general anaesthesia. Mean recovery times in the propofol group, required for patients to sit out of bed (44.8 minutes; SD 18.6) and meet discharge criteria (113.1 minutes; SD 34.5) were significantly (P less than 0.05) shorter than those in the thiopentone group (59.7 minutes; SD 21.4 and 133.5 minutes; SD 34.5). Fewer patients in the propofol group were treated in the recovery room for nausea and vomiting and the incidence of mild nausea not requiring treatment was less in the propofol group, but these differences were not statistically significant. Postoperative mental performance, measured by the FAST index, a new test of mental speed, was reduced on average by 1.7% of preoperative levels, during the recovery period tested, with no significant difference between the groups.

Adult↗
PubMed1991

Diagnosis of urinary tract infection in children: fresh urine microscopy or culture?

Fresh unspun and unstained urine specimens from 342 children with previous urinary tract infection (UTI) or symptoms compatible with a UTI were examined by microscopy at a magnification of x 400 in a mirrored counting chamber by a clinician, and sent for culture in a microbiology laboratory; 200 samples were also plated onto dip-slides. When microscopy and culture results were discrepant, further urine samples were collected until a diagnosis of UTI (24) or sterile urine (318) could be confirmed. Initial microscopy correctly identified 23 of 24 UTIs and 286 of 318 sterile urines; 1 false-positive result was caused by vaginal contamination with lactobacilli. 32 specimens (9%) gave an equivocal result on microscopy; the 1 other true-positive result was identified correctly on microscopy of the next urine specimen obtained. Culture of the initial urines correctly identified all 24 UTIs, but only 82% of the negative samples. Of the samples from uninfected children, 35 (11%) showed a mixed growth which was sterile on repeat sampling, and 21 (6.6%) initially grew a false-positive pure growth of more than 10(5) colony-forming units/ml of one organism. True UTIs were associated with bacterial counts above 10(7)/ml. Microscopy by a clinician represents a cheaper, quicker, and more reliable screening test for UTI in children than does routine culture in a microbiology laboratory.

Adolescent↗
PubMed1991

Urine collection from disposable nappies.

Urine was collected for microscopy and culture by standard use of sterile adhesive bags and by extraction from wet disposable nappies from 45 patients aged 1 to 23 months. Urine can readily be obtained by compression of wet nappy fibres within a 20 ml syringe if highly absorbent brands that contain gel beads are avoided. Red and white cell numbers were reduced on light microscopy of specimens obtained from nappies, but bacterial counts were unchanged. On culture, 6 children were shown to have urinary tract infections by both methods; of the children who did not have a urine infection, the contamination rate was lower from nappy collections (10/39 vs 17/39 from urine bags). Biochemical analysis of urine collected from 11 older children showed very close correlation for sodium, potassium, urea, and creatinine concentrations and osmolality between freshly voided urine and samples obtained after they were soaked into disposable nappies for 3 h and reclaimed, although there was greater variation for measurements of calcium and phosphate. Extraction of urine from disposable nappies put on within 4 h and which are not soiled by faeces is an inexpensive, rapid, and simple method to collect urine from young children for culture, microscopy for bacteria, and biochemical analysis.

Colony-Forming Units Assay↗