Search PubMed⌕ Search

Biomedical subjects

M Wall

Publications and source records attributed to M Wall.

At least 55 records · Page 3Linked to original sources
PubMed1997

Visual acuity scored by the letter-by-letter or probit methods has lower retest variability than the line assignment method.

PURPOSE: The optimal method for scoring visual acuity measures is unknown. Our goal was to determine, in a clinical setting, the method of scoring visual acuity with the lowest test-retest variability. METHODS: We investigated the effect of three different scoring methods using the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity chart comparing 32 patients with macular disease and 38 age-matched normal subjects. All subjects completed six repetitions of ETDRS charts. Three scoring methods were then used (line assignment, ETDRS or letter-by-letter and probit), the results were converted to log MAR values and the test-retest variabilities analysed. RESULTS: We found significant differences in variability among the three scoring methods (p < 0.0001). The variability was greatest with the line assignment method and less with the ETDRS and probit methods. The ETDRS and probit methods had similar variabilities. The difference in variability between normals and patients was not statistically significant. There were no differences in the calculated visual acuities among the three methods, only the variabilities. Using the ETDRS or probit methods, the within-test standard deviation was about 0.04 log MAR units (two letters). CONCLUSION: Test-retest variability of visual acuity measurements is lower using the ETDRS or probit methods than the traditional line assignment method.

Adult↗
PubMed1997

Prospective study of blunt aortic injury: Multicenter Trial of the American Association for the Surgery of Trauma.

BACKGROUND: Blunt aortic injury is a major cause of death from blunt trauma. Evolution of diagnostic techniques and methods of operative repair have altered the management and posed new questions in recent years. METHODS: This study was a prospectively conducted multi-center trial involving 50 trauma centers in North America under the direction of the Multi-institutional Trial Committee of the American Association for the Surgery of Trauma. RESULTS: There were 274 blunt aortic injury cases studied over 2.5 years, of which 81% were caused by automobile crashes. Chest computed tomography and transesophageal echocardiography were applied in 88 and 30 cases, respectively, and were 75 and 80% diagnostic, respectively. Two hundred seven stable patients underwent planned thoracotomy and repair. Clamp and sew technique was used in 73 (35%) and bypass techniques in 134 (65%). Overall mortality was 31%, with 63% of deaths being attributable to aortic rupture; mortality was not affected by method of repair. Paraplegia occurred postoperatively in 8.7%. Logistic regression analysis demonstrated clamp and sew (p = 0.002) and aortic cross clamp time of > or = 30 minutes (p = 0.01) to be associated with development of postoperative paraplegia. CONCLUSIONS: Rupture after hospital admission remains a major problem. Although newer diagnostic techniques are being applied, at this time aortography remains the diagnostic standard. Aortic cross clamp time beyond 30 minutes was associated with paraplegia; bypass techniques, which provide distal aortic perfusion, produced significantly lower paraplegia rates than the clamp and sew approach.

Adolescent↗
PubMed1997

Variability in patients with glaucomatous visual field damage is reduced using size V stimuli.

PURPOSE: To test the hypothesis that variability of conventional automated perimetry can be reduced using size V stimuli for patients with glaucomatous visual field damage. METHODS: Ten patients with glaucoma and five age-matched control volunteers were tested with the Humphrey Field Analyzer program 24-2 or 30-2, after which the method of constant stimuli was used to measure frequency-of-seeing curves. This was done by controlling the perimeter with a custom program run by a personal computer. At two widely separated visual field locations on the program 24-2 or 30-2 grid, stimuli were presented in 2 dB intervals to at least 10 dB on either side of the estimated program 24-2 or 30-2 threshold. This protocol was performed for each of three stimulus sizes (Goldmann sizes I, III, and V). For the patients with glaucoma, one test location was chosen in an area of normal visual field sensitivity, the other in an area of 10 to 20 dB loss. Control subjects were tested at the (3 degrees, 3 degrees) and (-21 degrees, -9 degrees) test locations. Fifteen repetitions were performed at each intensity. RESULTS: Repeated measures analysis of variance showed that variability, as measured by the standard deviation of the cumulative Gaussian function of the fitted frequency-of-seeing curves, was lowest at the abnormal sensitivity test location in the subjects with glaucoma using a size V stimulus. Differences between the results from the V to III and V to I stimuli were statistically significant (size V = 2.9 dB, III = 10.1 dB, I = 10.1 dB). The same trend in estimated standard deviations was present in tests of the area of normal sensitivity (size V = 1.1 dB, III = 1.7 dB, I = 2.0 dB) in subjects with glaucoma and for the control subjects' peripheral test locations, but not for the central location. The smaller reduction in variability between estimated standard deviations of the size I and size III stimuli was not statistically significant at any test location. CONCLUSIONS: Use of size V stimuli in conventional automated perimetry reduces variability in tests of moderately damaged and normal sensitivity test locations in subjects with glaucoma.

Analysis of Variance↗
PubMed1996

Malaria Prophylaxis in Different Age Groups.

Background: There is a perceived increased health risk in senior visitors to malaria endemic countries. Methods: The authors sought to compare effectiveness and tolerability of malaria chemoprophylaxis in senior travelers (>=60 years) with those in younger travelers (20-59 years). The "Malpro 2" database consists of more than 100,000 questionnaires completed by travelers on charter planes returning from East Africa to Europe during July 1988-December 1991. Among them, 9106 (9.1%) of the travelers were 60 years or older, and 84,562 (84.6%) of the travelers reported to be 20-59 years. Variables of demography, travel data, and the effectiveness and tolerability of chemoprophylaxis were compared in the two subgroups. Results: Malaria in Africa was reported by 8 (1/1000) elderly travelers and by 189 (2.2/1000) travelers aged 20-59 years. Adjusting for age, sex, prophylaxis, and duration of stay in Africa in a logistic regression model, malaria was significantly more frequent in younger than in senior travelers (p<.05). Any travel-associated illness was reported by 7.0% in the senior age group and by 13.6% in the younger age group (p<.05). The rates of travelers who indicated they had "side effects" attributable to malaria prophylaxis varied between 9.7% in the elderly and 15.5% in the younger travelers (p<.05). Conclusion: Senior travelers tolerate malaria chemoprophylaxis and visits to the tropics at least as well as younger travelers.

Journal Article↗
PubMed1996

Benefits of the placebo effect in the therapeutic relationship.

This paper starts by defining placebos, and describes several placebo effects observed in orthodox medicine. The authors argue that the concept of the placebo effect should not be confined to treatment and medicine alone, but should be extended to the therapeutic relationship itself. They maintain that the interpersonal skills practiced by the complementary therapist are a major factor in producing positive health outcomes. Furthermore, the personality, presentation, and demeanour of the complementary therapist are thought to play a vital part in the promotion of clients' psychological well-being. Other benefits of the placebo effect are discussed, including positive behaviour reinforcement resulting in the client's desire to return to the therapist for further consultation and treatment. The paper concludes by offering several ways in which the placebo effect can be established within the boundaries of the therapeutic relationship.

Holistic Nursing↗
PubMed1996

The psychometric function and reaction times of automated perimetry in normal and abnormal areas of the visual field in patients with glaucoma.

PURPOSE: To study the relationship of reaction time to the psychometric function in normal subjects, normal sensitivity test locations in patients with glaucoma, and test locations with 10 to 20 dB loss in patients with glaucoma. METHODS: The authors tested 10 patients with glaucoma and 10 age-matched normal volunteers with the Humphrey perimeter, first with program 24-2 and then with the method of constant stimuli to generate frequency of seeing curves. At two widely separated visual field locations on the program 24-2 grid, they presented stimuli in 2-dB intervals, 10 dB either side of the program 24-2 threshold, at 0 dB and 60 dB (15 repetitions per intensity). For the patients with glaucoma, they chose a visual field location with normal sensitivity and a location in an area of 10 to 20 dB loss. RESULTS: Analysis of variance with post hoc t-tests showed that reaction time (RT) at the 0-dB intensity was prolonged by approximately 90 msec in the abnormal sensitivity test location of patients with glaucoma compared to the control and the glaucoma normal sensitivity groups (P<0.0001). However, this difference was accounted for by only 4 of the 10 patients with glaucoma, reaching 100% of stimuli seen with the brightest stimulus at the moderately damaged test location. Reaction time at the frequency of seeing 50% estimated threshold showed no significant differences among the groups. Prolongation of RT from the 0-dB value was analyzed as a function of increasing attenuation of stimulus intensity. The results fit the equation RT = a + b(Intensity3) for all groups. CONCLUSIONS: There is no significant difference in RT between normal subjects and patients with glaucoma either at threshold or to suprathreshold stimuli. Reaction time increases after a power function with increasing attenuation of stimulus intensity up to the threshold.

Glaucoma, Open-Angle↗
PubMed1995

Idiopathic intracranial hypertension. Lack of histologic evidence for cerebral edema.

OBJECTIVE: To study brain histologic features in two cases of idiopathic intracranial hypertension (pseudotumor cerebri) at autopsy. DESIGN: Formaldehyde solution-fixed sections of cerebral white matter in two cases and structures of the sensory visual system in one case were analyzed. SETTING: University medical center. PATIENTS: Two patients with idiopathic intracranial hypertension who died unexpectedly. MAIN OUTCOME MEASURE: Histologic study of cerebral white matter in the two patients. RESULTS: We did not find histologic evidence of any type of cerebral edema in our patients. Review of a portion of the material from a previous report is also consistent with this conclusion. CONCLUSION: If patients with idiopathic intracranial hypertension have histologically apparent cerebral edema, it is not a consistent finding.

Adult↗
PubMed1995

The structure of Escherichia coli heat-stable enterotoxin b by nuclear magnetic resonance and circular dichroism.

The heat-stable enterotoxin b (STb) is secreted by enterotoxigenic Escherichia coli that cause secretory diarrhea in animals and humans. It is a 48-amino acid peptide containing two disulfide bridges, between residues 10 and 48 and 21 and 36, which are crucial for its biological activity. Here, we report the solution structure of STb determined by two- and three-dimensional NMR methods. Approximate interproton distances derived from NOE data were used to construct structures of STb using distance-geometry and simulated annealing procedures. The NMR-derived structure shows that STb is helical between residues 10 and 22 and residues 38 and 44. The helical structure in the region 10-22 is amphipathic and exposes several polar residues to the solvent, some of which have been shown to be important in determining the toxicity of STb. The hydrophobic residues on the opposite face of this helix make contacts with the hydrophobic residues of the C-terminal helix. The loop region between residues 21 and 36 has another cluster of hydrophobic residues and exposes Arg 29 and Asp 30, which have been shown to be important for intestinal secretory activity. CD studies show that reduction of disulfide bridges results in a dramatic loss of structure, which correlates with loss of function. Reduced STb adopts a predominantly random-coil conformation. Chromatographic measurements of concentrations of native, fully reduced, and single-disulfide species in equilibrium mixtures of STb in redox buffers indicate that the formation of the two disulfide bonds in STb is only moderately cooperative. Similar measurements in the presence of 8 M urea suggest that the native secondary structure significantly stabilizes the disulfide bonds.

Amino Acid Sequence↗
PubMed1995

Predictors of smoking during and after pregnancy: a survey of mothers of newborns.

BACKGROUND: Cigarette smoking during pregnancy represents a significant health risk to the fetus, but most women continue to smoke during pregnancy, and most who quit relapse postpartum. This study provides an assessment of psychosocial variables on women who quit, relapsed, cut down, or did not alter their smoking during pregnancy. METHODS: Mothers of newborns in 49 pediatric practices (N = 13,495) were surveyed at the newborns' first well-care office visit to a pediatrician, and 2,901 mothers who smoked in the month prior to pregnancy were identified. Predictive information was obtained by comparing mothers who quit smoking with those who continued to smoke, mothers who stayed quit with relapsers, and mothers who reduced tobacco consumption with those who did not. RESULTS: Thirty-five percent of mothers reported quitting smoking during pregnancy, and 52% had cut down for pregnancy. Factors related to quitting smoking for pregnancy were younger age, higher level of education, lower smoking level, having a partner who did not smoke, and not consuming alcohol. Mothers who quit also reported allowing less smoking in the home. Relapse for quitters was highly correlated with partner's smoking. For women who cut down but did not quit, smoking level and age were most significant.

Adult↗
PubMed1995

Random dot motion perimetry in patients with glaucoma and in normal subjects.

PURPOSE: To determine whether patients with primary open-angle glaucoma have an increase in size thresholds, prolongation of reaction times, and greater localization errors to random dot motion stimuli than normal subjects. METHODS: Motion perimetry, a computer graphics method of visual field testing, quantitates a subject's ability to detect a correlated shift in position of dots within a defined circular area against a background of fixed dots. We measured motion thresholds, the smallest detectable circular dot motion target, at the Humphrey 24-2 test loci. By using the subject's light-pen responses to the location of the targets, we computed motion size threshold, reaction times, and localization errors (number of pixels from where the subject touched the monitor to the target center). With motion perimetry and conventional automated perimetry, we tested one eye in each of 25 patients with primary open-angle glaucoma and 25 age-matched control subjects. We then generated total deviation pointwise probability plots for the patients with primary open-angle glaucoma. RESULTS: Patients with primary open-angle glaucoma had increased mean motion size threshold (P < .001) and increased localization errors (P < .002), compared with the control subjects. With the probability plot analysis, there was good correlation of the visual field defects between the two perimetry tests. Additionally, motion perimetry identified nerve fiber bundle-like defects in 12 patients that were not detected with conventional automated perimetry. CONCLUSIONS: Patients with primary open-angle glaucoma had abnormal motion perception with an increase in spatial localization error.

Adult↗
PubMed1995

Genetic diagnosis using polymerase chain reaction and fluorescent in-situ hybridization analysis of biopsied cells from both the cleavage and blastocyst stages of individual cultured human preimplantation embryos.

Cultured human preimplantation embryos have been used to develop methods which allow preimplantation genetic diagnosis (PGD) analyses by polymerase chain reaction (PCR) and fluorescent in-situ hybridization (FISH) on biopsied blastomeres and trophectoderm cells from the same embryo. An experimental design is described and experiments undertaken, which demonstrate the feasibility of extending biopsy and PGD procedures currently in use. We have shown that dual-stage biopsies are possible, and that the PCR and FISH analyses of the biopsied cell samples are effective. One to two blastomeres were biopsied from an 8- to 10-cell embryo and processed for the simultaneous PCR amplification of a beta-globin and a cytosine adenine (CA) repeat sequence, or a Y chromosome sequence. FISH procedures were also used to detect the presence of Y chromosome markers. The biopsied cleavage-stage embryo can be cultured to the blastocyst stage, where the serial biopsy of three to five mural trophectoderm cells provides two further cell samples. These can be used to repeat and/or undertake additional PGD analyses. The biopsied blastocyst is either used to confirm earlier diagnoses, or placed in culture for a further 4-24 h. Maintenance of a blastocoele cavity, hatching and formation of an outgrowth demonstrates continuing viability following the dual-stage biopsy procedures. The PCR DNA amplification procedures are effective at the cellular level for both biopsied blastomeres and mural trophectoderm cells. The FISH techniques have shown a definitive Y signal in 50% (one out of two) and 100% (two out of two) of the biopsied blastomeres and 72% (two out of three, four out of five and 7 out of 10) for the trophectoderm cell nuclei. Preliminary experiments have demonstrated that the FISH preparations can be re-amplified to improve the signal, and dual fluorescent procedures using the X and Y probes are effective. A retrospective PCR analysis has also been undertaken on preparations of biopsied cells which were previously used for PGD analysis by FISH.

Blastocyst↗
PubMed1995

A retrospective analysis of the in-vitro development of 'spare' human in-vitro fertilization preimplantation embryos using 'in-house' prepared medium and 'Medi-Cult' commercial medium.

In-house prepared medium was used routinely in our in-vitro fertilization (IVF) facility prior to the introduction of the commercial 'Medi-Cult' products. A comparative study of the in-vitro development of embryos cultured in two [T6 and Earle's balanced salt solution (EBSS)] human-inactivated serum (HIS)-supplemented media from days 0 to 5 showed that 44.7% (46/103) of the embryos developed to the blastocyst stage in the T6 medium compared with 22.3% (23/103) in EBSS. Following the introduction of the commercial Medi-Cult IVF M2 medium, which is used routinely to culture fertilized eggs from days 0 to 2, new baseline data were required for the in-vitro development of 'spare' embryos from days 2 to 5. When Medi-Cult M3 medium was used, 35.6% (37/104) of the 'spare' day 2 embryos achieved the blastocyst stage. However, if morphologically similar (four normal nucleated blastomeres with no fragmentation) day 2 embryos were selected, an increase in the blastocyst rate to 50.0% (33/66) was achieved. This compared favourably with the 45.0% blastocyst rate (published in the Medi-Cult literature) for M2/M3 medium cultured human embryos. A small series of experiments with T6 + HIS medium and human serum albumin (HSA)-supplemented Ham's F-10, MCDB 302 and M3 media was undertaken to identify a suitable medium which could be used for the culture of M2 medium day 2 embryos. Results show that M2 medium cultured embryos placed in Ham's F-10 medium supplemented with 10 mg/ml HSA gave an acceptable 37.8% (14/45) blastocyst rate. Therefore, this medium could be substituted for M3 medium in an emergency. A total of 483 IVF embryos donated by patients, which were surplus to the therapeutic IVF programme, were used for these studies over a period of 30 months. Late day 2 IVF spare embryos were assigned an embryo score based on a high-power phase-contrast microscopic examination prior to being placed in culture. The embryo score provides an effective in-vitro parameter with which embryos from different patients can be compared. The cleavage and development of individual embryos were monitored on days 2 to 5. In some cases, the continuing normal development and viability of the day 5 cultured embryo were assessed by monitoring the hatching, attachment and outgrowth of the cavitated blastocyst.

Blastocyst↗
PubMed1995

Using motion perimetry to detect visual field defects in patients with idiopathic intracranial hypertension: a comparison with conventional automated perimetry.

Motion perimetry, a method of visual field testing that uses computer graphics to measure motion perception, quantitates a subject's ability to detect a coherent shift in position of dots in a defined circular area against a background of fixed dots. Motion size threshold is defined as the smallest detectable circular target in which dot motion is detected. Subjects respond by touching a computer monitor screen with a light pen, first when they see a target (reaction time) and a second time where motion targets are detected (localization). Reaction time (msec) to the stimulus and localization error (number of pixels from target center) are then calculated and stored. We tested on eye in each of 20 idiopathic intracranial hypertension (IIH) patients and 40 age-matched normal subjects by conventional automated perimetry (Humphrey visual field analyzer, program 24-2) and motion perimetry. Pointwise probability plots of individual abnormal test points for size threshold responses were generated for the IIH patients based on the 95% confidence limits of the normal subject responses. An analysis of the subjects' visual field pairs (motion versus conventional automated perimetry) was performed based on these probability plots. The IIH patients had an elevated mean motion threshold (p < 0.001) and reaction time (p < 0.001) compared with the normal subjects. There were no significant differences for the localization errors. Based on the probability plot analysis, there was good correlation of the visual field defects between the two perimetry tests. In addition, motion perimetry identified nerve fiber bundle-shaped defects in nine patients in whom they were not detected with conventional automated perimetry.

Adult↗
PubMed1995

Pattern of axonal loss in longstanding papilledema due to idiopathic intracranial hypertension.

There is both clinical and histopathologic evidence for peripheral visual field loss and optic nerve degeneration in longstanding papilledema due to idiopathic intracranial hypertension (IIH). The purpose of this study was to look at the extent and distribution of axonal dropout in secondary optic atrophy due to IIH. Both optic nerves from a 29-year-old man with a two year history of IIH were examined histologically and morphometrically. A high-contrast lipid (myelin) stain, paraphenylenediamine (PPD), and a semiautomated image analysis system were employed to resolve sufficiently the optic nerve fiber images for counts and for measurement. There were 80% and 90% losses of axons, respectively, in the right and left optic nerves consequent to IIH. The axonal loss in the peripheral area of each optic nerve was much more severe than that in inner sectors (= 0.001 for the right optic nerve and = 0.005 for the left). This pattern of axonal dropout is consistent with the preservation of good central visual acuity despite devastating optic nerve atrophy, and with the severe peripheral visual field loss noted in this patient.

Adult↗
PubMed1995

Idiopathic intracranial hypertension.

Although the cause of IIH remains obscure, it has become clear that loss of visual function is common and patients may progress to blindness. Diagnosis should adhere to the modified Dandy criteria. Recent case-control studies cast doubt on the validity of many frequently cited conditions associated with IIH. Valid associations include obesity, recent weight gain, female gender, vitamin A intoxication, and steroid withdrawal. IIH patient management should include serial perimetry using a sensitive disease-specific strategy. This is done so the proper therapy can be selected and visual loss prevented or reversed.

Adolescent↗