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Biomedical subjects

M Wall

Publications and source records attributed to M Wall.

At least 37 records · Page 2Linked to original sources
PubMed1999

Serum vitamin A concentration is elevated in idiopathic intracranial hypertension.

OBJECTIVE: The primary purpose was to investigate whether serum vitamin A concentration is associated with idiopathic intracranial hypertension (IIH). The secondary aim was to obtain pilot data regarding the amount of vitamin A ingested by patients and controls. BACKGROUND: Vitamin A is an attractive candidate mediator of IIH as many of the symptoms and signs of hypervitaminosis A mimic those of IIH. METHODS: We prospectively determined serum retinol and retinyl ester concentration in 16 women with IIH and 70 healthy young women. Using a survey instrument, we also determined the average daily vitamin A ingestion in a convenience sample of patients and controls. RESULTS: Serum retinol concentration was significantly higher in the patient group (median 752 ug/L) compared with the control group (median 530 ug/L), even after adjusting for age and body mass index (p < 0.001). Retinyl ester concentration, however, was similar in the patient (median 48 ug/L) and control (median 41 ug/L) groups (p = 0.32). There was no significant correlation between serum retinol concentration and body mass index in the patients (r = 0.16) or controls (r = -0.02). Finally, there was no significant difference in the amounts of vitamin A ingested by the patients or controls, although the small number of subjects in both groups reduced the power of this conclusion. CONCLUSIONS: Elevated serum retinol concentration is associated with IIH. Obesity, by itself, does not explain these higher levels. Patients may ingest an abnormally large amount of vitamin A, metabolize it abnormally, or be unusually sensitive to its effects. Alternatively, elevated level of serum retinol may reflect an epiphenomenon of another variable we did not measure or a nonspecific effect of elevated retinol binding capacity.

Adolescent↗
PubMed1999

Automated perimetry in amblyopia: a generalized depression.

PURPOSE: To quantitate the visual field abnormalities associated with amblyopia. METHODS: In a prospective study, 37 amblyopic patients (11 anisometropic, 13 strabismic, 9 combination, 4 deprivation) performed automated perimetry in each eye using the Humphrey 30-2 program. Primary outcome measures were foveal threshold, mean deviation, and average threshold. RESULTS: When the probability plots were examined, 21 visual fields in amblyopic eyes were normal, 8 had central scotomas, and 7 had diffuse depressions. No focal defects other than mild central scotomas were seen. However, the foveal threshold of amblyopic eyes was decreased by an average of 7.2 +/- 8.0 dB (P < .0001) compared with fellow eyes; intereye differences in mean deviation (3.2 +/- 5.4 dB; P < .001) and average threshold (2.9 +/- 5.3 dB; P < .005) were also seen. This decrease in sensitivity for the amblyopic eye occurred for all types of amblyopia. The depression in threshold was greatest at the fovea but was detectable and significant at all eccentricities of the 30-degree field. The average threshold in the amblyopic eye was highly correlated with visual acuity (r = .839; P < .001). CONCLUSIONS: Although automated visual fields in amblyopic eyes typically appear normal, all four types of amblyopia are associated with a generalized depression of light sensitivity, which is proportionately greatest at the fovea and highly correlated with visual acuity loss. In general, amblyopia is not associated with any area of focal loss of threshold light sensitivity. If a focal defect is present in the visual field of the amblyopic eye, organic causes of visual loss should be suspected. The Humphrey visual field analyzer STATPAC program (Allergan-Humphrey, Inc, San Leandro, California) may artifactually transform small and generalized full-field depressions in a manner that makes them appear to be isolated central defects.

Adult↗
PubMed1999

Multibubble sonoluminescence in aqueous salt solutions.

The sonoluminescence from aqueous solutions containing various salts in the concentration range of 0 to 7 M has been examined using 3.5 ms pulses of 515 kHz ultrasound. In almost all cases the sonoluminescence intensity recorded increased with increasing salt level until a critical concentration (in the range of 1-2 M) was reached. At salt levels above the critical concentration the signal intensity decreased sharply with increasing salt concentration. It is not possible to satisfactorily account for the trends in terms of changes in solution viscosity, rate of bubble coalescence, water vapour pressure, air/water interfacial tension or ionic strength. However, a good correlation of the increase in the signal with the extent of gas solubilisation in the solutions with changing salt concentration was observed. Possible reasons for the signal increase with the addition of salts and the marked decrease at high salt concentrations are discussed.

Journal Article↗
PubMed1999

Random dot motion stimuli are more sensitive than light stimuli for detection of visual field loss in ocular hypertension patients.

PURPOSE: To determine whether motion detection perimetry or luminance size threshold perimetry (a test using the motion perimetry method with luminance stimuli) is more sensitive in detecting visual loss in ocular hypertension patients. METHODS: Motion perimetry uses a customized computer graphics program to detect a subject's ability to identify a coherent shift in position of moving dots in a defined circular area against a background of fixed dots. Motion size threshold is defined as the smallest circular area within which dot motion is detected. Patients respond by touching the area of the computer monitor where they perceive the stimulus with a light pen. The localization errors are measured as the number of pixels from target center for each trial. Luminance size threshold perimetry uses the same technique except the background is dark gray and the stimuli are filled lighter gray circles. We tested one eye in each of 27 ocular hypertension patients and 27 age-matched normal subjects with both tests. Our main outcome measures were motion and luminance size thresholds, total deviation probability plot data, and spatial localization errors. RESULTS: With the total deviation probability plot analysis, the ocular hypertension patients had a greater number of abnormal test locations with motion perimetry stimuli than with luminance stimuli. The abnormal test points were located most often in the superior and inferior nasal regions. Six subjects had nerve fiber bundle-like defects to motion stimuli whereas three patients had defects with luminance size threshold perimetry. The ocular hypertension patients had significantly greater localization errors than the controls with both tests. CONCLUSIONS: Using a size thresholding technique in ocular hypertension patients, random dot motion stimuli appear to be more sensitive than luminance stimuli. Errors in stimulus localization are significantly increased in ocular hypertension patients, independent of the stimulus (motion or luminance) used.

Adult↗
PubMed1999

Normal aging effects for frequency doubling technology perimetry.

PURPOSE: To determine the influence of normal aging on contrast sensitivity for frequency doubling technology (FDT) perimetry. METHODS: Contrast sensitivity measures were obtained for frequency-doubled stimuli (0.25 cycles per degree sinusoidal gratings undergoing 25 Hz counterphase flicker) at 17 target locations (4 per quadrant plus the central 5 degrees ) using a prototype of the Welch Allyn (Skaneateles, NY)/Humphrey Systems FDT perimeter (Humphrey Systems, Dublin, CA). A total of 407 normal subjects (761 eyes) between the ages of 15 and 85 years were tested. RESULTS: Between the ages of 15 and 60 years there was an approximately linear decrease in contrast sensitivity of 0.6 dB per decade. After the age of 70, there was a slightly greater sensitivity loss with age. There were no meaningful differences in sensitivity loss as a function of age for different visual field locations. A small but consistent reduction in contrast sensitivity (approximately 0.7 dB) was found at all visual field locations for the second eye tested that may be due to a central adaptation process. CONCLUSIONS: Normal aging effects for FDT perimetry are similar to those obtained for conventional automated perimetry, except that the FDT perimetry aging effects do not appear to be eccentricity dependent. These normative data provide a basis for establishing a statistical analysis procedure and probability plots for FDT perimetry.

Adolescent↗
PubMed1999

Differential patterns of executive function in children with attention-deficit hyperactivity disorder according to gender and subtype.

The present investigation examined differential patterns in executive functions of children with attention-deficit hyperactivity disorder (ADHD; no diagnosed comorbid disorders) according to subtype and gender, and identified instrumentation sensitive to executive function in children aged 6 to 12 years with ADHD. Data were obtained from 94 children diagnosed with ADHD (predominantly inattentive, n = 32, ADHD combined, n = 62), and from 28 controls. Participants with ADHD, who were unmedicated at the time of testing, were administered five tests of executive function (the Wisconsin Card Sorting Test, the Stroop Color-Word Test, the Matching Familiar Figures Test, the Trail Making Test, and the Tower of London). A two-way multivariate analysis of covariance with age as the covariate and subtype and gender as the independent variables was conducted on all of the tests administered. While children with ADHD predominantly inattentive and those with ADHD combined differed from controls, it was only the latter subtype that differed significantly in perseveration and response inhibition. The absence of diagnosed comorbidity in the children with ADHD at the time of test administration demonstrates that the impairments in executive function are clearly located in ADHD, particularly in the ADHD combined subtype, thus providing support for Barkley's proposed unifying theory of ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed1998

Long- and short-term variability of automated perimetry results in patients with optic neuritis and healthy subjects.

OBJECTIVE: To measure the short- and long-term variability of automated perimetry in patients with optic neuritis and normal subjects. DESIGN: Prospective case-control design of patients with recovered optic neuritis with intraday and interday repetitions to obtain robust variability measurements. Entry criteria included a corrected pattern SD that was worse than the normal 5% probability level and a mean deviation worse than -3 dB but better than -20 dB. Five Humphrey 30-2 full threshold tests were administered during a 7-hour period (1 test every 2 hours) on the same day and at the same periods on 5 separate days. SUBJECTS: Seventeen patients with recovered optic neuritis and 10 healthy subjects of similar age. MAIN OUTCOME MEASURES: Short-term variability and long-term variability for global visual field data. RESULTS: Patients with optic neuritis demonstrated variations in visual field sensitivity that were outside the entire range of variability for normal controls. These variations occurred for multiple tests performed on the same day at specific times and for tests performed at specific times on different days. There were no consistent patterns of sensitivity changes that could be attributed to time of day. The most dramatic fluctuations occurred in a patient whose visual fields varied from normal to a hemianopic defect from one week to another and from a partial quadrant loss to a hemianopic defect at different times on the same day. Seven of the patients with optic neuritis also demonstrated intermittent vertical step defects. CONCLUSIONS: Patients with resolved optic neuritis can have large variations in visual field results on different days and at different times on the same day. The variations affect both the severity and the pattern of visual field loss and do not appear to be consistent across patients. These data indicate that care must be taken when automated visual field results in patients with optic neuritis are interpreted. Distinguishing systematic changes in sensitivity from variability requires more than a comparison of the current visual field with the most recent previous visual field.

Adult↗
PubMed1998

Motion perimetry in anisometropic amblyopia: elevated size thresholds extend into the midperiphery.

PURPOSE: Our purpose was to determine whether motion detection abnormalities in patients with anisometropic amblyopia exist and to determine the extent of these abnormalities in the central and midperipheral visual field. METHODS: We used of motion perimetry to evaluated 10 anisometropic subjects with no manifest strabismus. Each of 44 locations in the visual field corresponding to the test sites of the Humphrey 24-2 program was tested with circular patches of motion (random dot cinematograms) displayed on a computer screen. Stimulus patch size was reduced in a 2/1 staircase manner to determine the smallest patch of motion detectable at each test location (threshold). Data from 15 age-matched normal subjects were used as controls. RESULTS: Vision in the amblyopic eye ranged from 20/25 to count fingers. The overall mean size threshold for amblyopic eyes was elevated (61% +/- 73%) compared with fellow eyes and age-matched normal eyes (p < 0.03) (i.e., the moving patch of dots in the field had to be larger for it to be detected when viewing with the amblyopic eye). The increase in size threshold was consistent across the visual field and was not greater for central locations. CONCLUSION: The amblyopia caused by anisometropia is associated with an abnormality in motion detection that extends into the midperiphery of the visual field.

Amblyopia↗
PubMed1998

Risk moderation of parent and child outcomes in a preventive intervention: a test and replication.

Family risk-related variations in proximal parent and young adolescent outcomes of a universal family-focused preventive intervention were examined using a cumulative index of risk incorporating sociodemographic characteristics and social-emotional adjustment measures. Results of an initial investigation involving 209 families of young adolescents suggested that intervention efficacy was largely unrelated to cumulative family risk. These findings were replicated with a second sample of 428 families. Implications for future intervention applications and outcome research are discussed.

Adolescent↗
PubMed1998

Proximal and distal histidines in thyroid peroxidase: relation to the alternatively spliced form, TPO-2.

The distal and proximal histidines in thyroid peroxidase (TPO), located by amino acid sequence alignment with their known counterparts in myeloperoxidase, are His 239 and His 494, respectively. These histidines lie outside the 57 amino acid peptide (residues 533-589) that is absent in the alternatively spliced form, TPO-2. However, asparagine 579, which very likely forms a stabilizing hydrogen bond with the proximal histidine in TPO, lies within the missing peptide region. The absence of Asn 579 from TPO-2 may be at least partially responsible for the reported lack of activity of this form of the enzyme. Formation of TPO compound I may also depend on Arg 396, based on analogy with the catalytic mechanism previously proposed for the more widely studied plant and fungal peroxidases. A multiple sequence alignment prepared with five mammalian and five invertebrate peroxidases shows complete conservation of Arg 396, as well as residues corresponding to His 239, His 494, and Asn 579 in TPO. The animal peroxidases comprise a family of homologous proteins that differ markedly from the plant/fungal/bacterial peroxidases in primary, secondary, and tertiary structure, yet share with them a common function. Animal peroxidases probably arose independently of the plant/fungal/bacterial peroxidase superfamily and most likely belong to a different gene family. The relation between animal and nonanimal peroxidases may represent an example of convergent evolution to a common enzymatic mechanism.

Alternative Splicing↗
PubMed1998

Effects of weight loss on the course of idiopathic intracranial hypertension in women.

OBJECTIVE: To determine the role of weight loss in the treatment of idiopathic intracranial hypertension (IIH) in obese women. METHODS: Chart review of 250 patients with suspected IIH revealed 58 women who met our criteria, did not undergo early surgical intervention, and had adequate documentation of visual status, papilledema, and weight at the baseline evaluation and at 6 months or longer. Patients were divided into two groups based on whether weight loss > or = 2.5 kg occurred during any 3-month interval. Papilledema grade, visual acuity, and visual field grade at 6 months or longer and the time to improve each were recorded. RESULTS: Mean time in months to improve one grade for papilledema and visual field in one eye was 4.0 versus 6.7 (p = 0.013) and 4.6 versus 12.2 (p = 0.032), respectively, for the 38 patients with weight loss compared with the 20 patients with no weight loss. Papilledema resolved in 28/38 with weight loss (mean, 7.6 months) and 8/20 without weight loss (mean, 10.2 months; p = 0.352). There were no differences in final visual acuity or visual field between the two groups, but the papilledema grade was slightly better in the worst eye in each patient at baseline in the weight loss group (p = 0.03). CONCLUSIONS: Weight reduction is associated with more rapid recovery of both papilledema and visual field dysfunction in patients with IIH compared with those who do not lose weight.

Adolescent↗
PubMed1998

Asymmetric papilledema in idiopathic intracranial hypertension: prospective interocular comparison of sensory visual function.

PURPOSE: Visual loss is the main morbidity of idiopathic intracranial hypertension (IIH). The relationship between papilledema grade and visual loss is unclear. The goal of this study was to determine whether there is a relationship between papilledema grade and visual loss. METHODS: Fundus photographs of 478 patients with IIH were reviewed, and their degree of papilledema was graded using Frisén's scheme. We identified 46 patients (10%) with IIH and highly asymmetric papilledema, as defined by an interocular difference of two or more grades. Nine of these patients with active asymmetry agreed to return for a series of visual tests. They underwent three visual field tests-Humphrey visual field analyzer 24-2, motion perimetry, and ring perimetry. The perimetry outcome measures were mean deviation, foveal threshold, and means for eccentric zones (3 degrees, 9 degrees, 15 degrees, and 21 degrees). The patients participated also in visual acuity, Farnsworth-Munsell 100-hue, Pelli-Robson contrast sensitivity, and foveal flicker fusion testing. Their relative afferent pupillary defect was graded using neutral density filters. RESULTS: The intereye comparisons showed vision to be worse in the eye with the high-grade papilledema for all outcome measures. The magnitude of the loss with the perimetry tests increased with eccentricity. The measures of central visual function, although in the normal range, were relatively depressed in the eye with high-grade papilledema. CONCLUSIONS: Visual loss in patients with asymmetric papilledema caused by IIH was most pronounced in the eye with the higher grade of papilledema. Foveal visual functions, although they remained in the normal range, were also decreased in patients with high-grade papilledema. In patients with high-grade papilledema, visual loss appeared to affect the entire visual field, and the peripheral field showed the most deficit. Our findings showed that high-grade papilledema was associated with visual dysfunction in patients with IIH.

Adult↗
PubMed1997

Tolerability and Effectiveness of Malaria Chemoprophylaxis with Mefloquine or Chloroquine with or without Co-medication.

Background: To determine the relevance of drug interactions with co-medication for effectiveness and tolerability of antimalarial chemoprophylaxis. Method: A database (MALPRO2) on travelers on their flight home from Africa to Europe between July 1988 and December 1991 was reanalyzed. It contains data on prophylaxis with mefloquine (n = 48,264), with chloroquine (6,752), with chloroquine plus proguanil (19,727), and with no prophylaxis (3,871). The comparison of rates of malaria incidence and adverse events (AEs) between users and nonusers of co-medication was expressed by relative risk (RR). Results: Fifty-three percent of travelers (63% of females, 43% of males) used co-medication in all prophylaxis groups, with an average of 1.35 additional drugs per person and about two AEs reported per person. With the exception of antidiarrheals plus mefloquine, malaria incidence with co-medication was lower (RR = 0.8) than without co-medication. In all regimens, the proportion of travelers reporting AEs was about 1.5-fold with co-medication (p<.01); that reporting severe AEs was twice as high as compared to with no co-medication. Mefloquine AE rates for various classes of co-medication were similar to that of chloroquine, with highest AE and severity rates with neuropsychiatric drugs (excluding antiepileptics, RR = 1.9 and 2.9), and lowest rates with cardiovasculars (RR = 1.1 and 1.0). Various co-medications were used with different frequencies in males and females, and the latter reported more AEs. Conclusion: These data suggest that co-medications commonly used by travelers have no significant clinical impact on safety and effectiveness of prophylaxis with mefloquine or chloroquine. Increased frequency and severity of AEs when using co-medication rather is explained by underlying illness.

Journal Article↗
PubMed1997

Central venous catheters coated with minocycline and rifampin for the prevention of catheter-related colonization and bloodstream infections. A randomized, double-blind trial. The Texas Medical Center Catheter Study Group.

BACKGROUND: Central venous catheters are a principal source of nosocomial bloodstream infections, which are difficult to control. OBJECTIVE: To determine the efficacy of catheters coated with minocycline and rifampin in preventing catheter-related colonization and bloodstream infections. DESIGN: Multicenter, randomized clinical trial. SETTING: Five university-based medical centers. PATIENTS: 281 hospitalized patients who required 298 triple-lumen, polyurethane venous catheters. INTERVENTION: 147 catheters were pretreated with tridodecylmethyl-ammonium chloride and coated with minocycline and rifampin. Untreated, uncoated catheters (n = 151) were used as controls. MEASUREMENTS: Quantitative catheter cultures, blood cultures, and molecular typing of organisms to determine catheter-related colonization and bloodstream infections. RESULTS: The group with coated catheters and the group with uncoated catheters were similar with respect to age, sex, underlying diseases, degree of immunosuppression, therapeutic interventions, and risk factors for catheter infections. Colonization occurred in 36 (26%) uncoated catheters and 11 (8%) coated catheters (P < 0.001). Catheter-related bloodstream infection developed in 7 patients (5%) with uncoated catheters and no patients with coated catheters (P < 0.01). Multivariate logistic regression analysis showed that coating catheters with minocycline and rifampin was an independent protective factor against catheter-related colonization (P < 0.05). No adverse effects related to the coated catheters or antimicrobial resistance were seen. An estimate showed that the use of coated catheters could save costs. CONCLUSIONS: Central venous catheters coated with minocycline and rifampin can significantly reduce the risk for catheter-related colonization and bloodstream infections. The use of these catheters may save costs.

Adolescent↗
PubMed1997

Motion perimetry identifies nerve fiber bundlelike defects in ocular hypertension.

OBJECTIVE: To determine whether patients with ocular hypertension (OHT) have elevated motion perimetry thresholds. DESIGN: Motion perimetry uses a customized computer graphics program to detect the ability to identify a coherent shift in position of 50% of dots in a defined circular area against a background of fixed dots. Motion size threshold is defined as the smallest circular area in which dot motion is detected. Subjects respond by touching the area of the computer monitor with a light pen where motion stimuli are perceived. Reaction times (milliseconds) to stimuli and localization error (number of pixels from target center) are also obtained for each trial. SETTING: University hospital ophthalmology clinic. PATIENTS OR OTHER PARTICIPANTS: Twenty-seven patients with OHT and 27 age-matched normal subjects. One eye was tested in each subject. MAIN OUTCOME MEASURES: Random dot motion stimuli size thresholds and total deviation probability plot data, reaction times, and spatial localization errors. RESULTS: The patients with OHT had more abnormal test points in the total deviation probability plot analysis compared with the controls (P < .001, chi 2). The abnormal test points were concentrated in the superior and inferior nasal regions. Six subjects had nerve fiber bundlelike defects to motion stimuli. Six subjects (5 overlapping with the probability plot analysis) had abnormal glaucoma hemifield test results. The patients with OHT also had significantly greater localization errors. CONCLUSION: Motion threshold perimetry may be a more sensitive method to detect visual field abnormalities in OHT than conventional automated perimetry.

Adult↗
PubMed1997

Luminance contrast and colour contrast related errors in pseudoisochromatic plate identification.

PURPOSE: To determine whether differences in luminance contrast and colour contrast are factors in failing to identify American Optical pseudoisochromatic plates (AOPP). METHODS: We studied two groups of subjects. In 20 normal test subjects with no errors on the AOPP we used cross-polarising filters to darken and then gradually increase perceived luminance of the AOPP until these normal subjects correctly identified the plate. In a second group, to evaluate the relationship between a luminance contrast sensitivity score using Arden plates and AOPP identification, we tested 37 non-colour-deficient subjects who missed zero to five of the AOPP of low colour and luminance contrast (plates 9-12, 15). RESULTS: Using the cross-polarising filters, we found five plates that required more light to identify (plates 9-12, 15). In the second experiment, we found a significant relationship between the number missed of these five AOPP plates and a decrease in contrast sensitivity (r = 0.91, p < 0.001, Spearman correlation coefficient). CONCLUSION: Errors in AOPP colour plate detection may be due to loss of ability to perceive colour contrast and possibly luminance contrast.

Adult↗