Exploring sequential stereopsis for co-planarity tasks

We used the sequential stereopsis paradigm and apparatus described by Enright (Vision Research, 36, (1996) 307-312). The observer's task was to set targets to equidistance in Experiments 1-3, and to make them co-planar in Experiment 4. However, it is argued that in all experiments observers exploited a co-planarity setting strategy. Sequential stereopsis produced good performance throughout in terms of low disparity thresholds when head position was varied by rotations around three axes: vertical (azimuth condition); horizontal (elevation); and midline (tilt). It also produced good performance when the targets were shifted in position so that they both lay on one side of the median plane of the head. These results cannot be accounted for by Enright's isovergence hypothesis unless it is extended to incorporate other information about eye positions. Performance was better but not greatly so in control simultaneous stereopsis conditions, nor did it deteriorate much when the observer's view was restricted solely to the targets by removing visibility of the room in which the apparatus was located. Target settings were typically located on a concave arc centred on the median plane. This effect was quantitatively modelled using disparity correction for a relief task of co-planarity (Gârding, Porrill, Mayhew, & Frisby. Vision Research, 35 (1995) 703-722). This modelling indicated over-estimations of c.10-20 cm in fixation distance for target distances in the range 71.5-112.5 cm.

Isolation and identification of a degradation product in a capsule formulation containing the elastase inhibitor, DMP 777

An unexpected degradation product, greater than 0.10%, was observed in a DMP 777 capsule formulation stored at 40 degrees C/75% r.h. for 3 months and 25 degrees C/60% r.h. for 2 years. The degradant of interest was prepared in quantity by refluxing the drug substance in dilute acid. A preparative HPLC method was developed to separate the various degradants and to collect each as a separate fraction. Each fraction was analyzed by the analytical HPLC gradient test method to assure positive identification of each peak and to correlate each peak to the original capsule sample. Key isolated degradation products were used for structure elucidation with mass spectrometry and NMR. The major degradant of interest in the capsule formulation was found to be a carboxylic acid resulting from the acid hydrolysis of an amide bond.

Segmental phenolic ablation for ingrown toenails in general practice

Ingrown toenails cause a great deal of discomfort and may result in missed time from school, work and sports. Traditionally, this problem was quickly dealt with by a simple nail avulsion or wedge avulsion in general practice, Accident and Emergency departments or O.P.D.s. However, this treatment has a high relapse rate (73%). In this survey ingrown toenails were treated by wedge resection and ablation of the nail bed with 80% fresh phenol under ring block anaesthesia and a bloodless field. The aim of this prospective study was to assess the feasibility, cure rate and complications of Segmental Phenolic Ablation for ingrown toenails in general practice. A prospective analysis of 201 consecutive Wedge Resections and Phenol Ablations for ingrown toenails in 111 patients by one General Practitioner over a five and a half year period. All patients were followed up for at least six months post-operatively. There was a relapse rate of 4.5%. Two-thirds of the recurrences occurred in patients who had relapsed after previous surgery before entering this study. All recurrences were successfully treated by repeat phenol cauterisation. The relapse rate for cases who had never been previously operated on (137 edges) was 2.2% (3 edges). There were no major peri-operative or post-operative complications. No patient had to be referred to hospital for treatment of their ingrown toenails. Wedge Resection and Phenol Ablation for ingrown toenails can be carried out safely and successfully in general practice and is recommended as the surgical treatment of choice.

Determinants of object recognition

We demonstrate that performance on an object recognition task can be explained in terms of observer-specific perceptual profiles. These profiles are derived from a battery of tests, including the effects of stereo, texture, outline (occluding contour), and motion cues on amplitude judgements of curved surfaces. Using a task in which observers learned to recognise 'amoeboid' objects, a multivariate regression analysis revealed that three psychometric variables derived from the test battery account for 74% of the variance in learning rate. These variables are choice reaction time, and the relative dependence of amplitude judgements on motion and outline cues. The implications of these findings for the existence of observer-specific perceptual profiles, and their relation to the fundamental psychophysical competences associated with object recognition are discussed.

Magnetic resonance imaging screening in women at genetic risk of breast cancer: imaging and analysis protocol for the UK multicentre study. UK MRI Breast Screening Study Advisory Group

The imaging and analysis protocol of the UK multicentre study of magnetic resonance imaging (MRI) as a method of screening for breast cancer in women at genetic risk is described. The study will compare the sensitivity and specificity of contrast-enhanced MRI with two-view x-ray mammography. Approximately 500 women below the age of 50 at high genetic risk of breast cancer will be recruited per year for three years, with annual MRI and x-ray mammography continuing for up to 5 years. A symptomatic cohort will be measured in the first year to ensure consistent reporting between centres. The MRI examination comprises a high-sensitivity three-dimensional contrast-enhanced assessment, followed by a high-specificity contrast-enhanced study in equivocal cases. Multiparametric analysis will encompass morphological assessment, the kinetics of contrast agent uptake and determination of quantitative pharmacokinetic parameters. Retrospective analysis will identify the most specific indicators of malignancy. Sensitivity and specificity, together with diagnostic performance, diagnostic impact and therapeutic impact will be assessed with reference to pathology, follow-up and changes in diagnostic certainty and therapeutic decisions. Mammography, lesion localisation, pathology and cytology will be performed in accordance with the UK NHS Breast Screening Programme quality assurance standards. Similar standards of quality assurance will be applied for MR measurements and evaluation.

Cryosurgery treatment of plantar warts

Plantar warts are common, painful and contagious. Because of their dept of penetration, self treatment with topical creams and gels is often very slow and commonly unsuccessful. Surgical excision or cautery are very painful, can leave permanent tender scars and often lead to relapse because of the Koebner phenomenon. 100 consecutive patients with plantar warts treated by one General Practitioner over a sixteen month period were analysed. Patients were followed up to assess success and relapse rates and the development of any complications. The number, type, size and position of plantar warts were also recorded and analysed. A total of 514 plantar warts presented for treatment. 505 Plantar Warts in 96 patients were considered suitable for treatment using liquid nitrogen cryosurgery via a Byrmill cryogun. Patients were treated by the open spray technique after debulking the plantar wart using a surgical blade. 421 plantar warts (83.5%) cleared completely with one single treatment of cryosurgery. A further 30 (6%) cleared with two treatments and another 15 (3%) cleared with three treatments. In total, 467 plantar warts (92.5%) cleared completely using cryosurgery and 90% of these cleared with one treatment. Of the remaining 38 plantar warts, 23 (4.5%) were lost to follow up and 12 (2.4%) were managed using other techniques after initially being treated with cryosurgery. Only 3 (0.6%) plantar warts failed to clear. However, all three were smaller and less painful after treatment. No patient had to be referred to hospital for treatment of their plantar warts. There were no serious complications of treatment. This study highlights the advantages of cryosurgery for treating plantar warts in general practice. This technique is quick, safe, highly successful, has a low relapse rate and leaves little or no scars.

Factors associated with reintegration to normal living after subarachnoid hemorrhage

OBJECTIVE

Recent reports have suggested improvement in the last decade in global outcome measures after subarachnoid hemorrhage (SAH), particularly in patients presenting in good initial neurological status. We used a standardized self-report instrument, the Reintegration to Normal Living (RNL) Index, to assess a patient-based quality of life measure and a self-report of work status. We tested the hypothesis that several patient-based factors were related to these outcomes, including depressive symptoms, physical disability, age, and initial Hunt and Hess grade. Using these data, we report the total management morbidity and mortality at 1 to 5 years after SAH for patients initially presenting in good neurological condition.

METHODS

The study population consisted of 246 consecutive patients admitted to our tertiary care center with aneurysmal SAH in good neurological condition (Hunt and Hess Grades I-III). Patients underwent either surgical (92%), endovascular (7%), or medical (1 %) management of aneurysmal SAH. Eighty-three percent of surviving patients completed a written or telephone questionnaire incorporating the Barthel Index, the Zung Self-rating Depression Scale, the RNL Index, and a work status assessment.

RESULTS

An aneurysm-related mortality rate of 6% was observed in the patient population. Fifty-five percent of patients reported a complete reintegration into their normal living situation, as measured by the RNL Index. Sixty-seven percent of previously full-time workers returned to a full-time status. Thirty-six percent of patients reported depressive symptoms, and 23% of patients reported physical disability. In a multivariate model, the two factors that contributed most to an impairment of reintegration were depression and physical disability, whereas a failure to return to work was related to older age and a higher-grade initial neurological status.

CONCLUSION

In this series of patients undergoing multimodality management of lower-grade SAH, more than one-half of patients subsequently reported a normal reintegration into their social situation, as assessed by the RNL Index. Standardized assessments of cofactors associated with impaired reintegration revealed that depressive symptoms and physical disability played a strong role in overall reintegration. Standardized assessments, such as the RNL Index, offer the potential for improved comparison of different treatment regimens and specific therapeutic targeting of factors, such as depression, which contribute to decreased quality of life.

A cell viability assay based on monitoring respiration by optical oxygen sensing

A cell viability assay based on monitoring of the metabolic activity of living cells via their consumption of dissolved oxygen has been developed. It uses a microwell plate format and disposable phosphorescent sensor inserts incorporated into each sample. The wells are subsequently sealed from ambient oxygen using a layer of mineral oil, and periodically scanned from underneath with a simple fiber-optic phosphorescent phase detector. Thus, dissolved oxygen levels and time profiles of cell respiration can be determined noninvasively and compared to each other. The system was tested by monitoring the viability of the fission yeast Schizosaccharomyces pombe. In comparison with the conventional cell densitometry assay, the optical oxygen sensor method could reliably monitor lower numbers of cells (10(4)-10(5) vs 10(6)-10(7) cells/ml for densitometry), and accurately determine culture viability within 1 h. The assay was then applied to determine the viability of samples treated with toxic agents such as azide and in response to expression of a physiological inducer of cell death, the Bcl-2 family member Bak. The results obtained confirm that measurement of cell respiration by this assay can serve as a predictable, reliable, and fast method for high-throughput determination of cell viability and growth.

A neoadjuvant clinical trial in colorectal cancer patients of the human anti-idiotypic antibody 105AD7, which mimics CD55

Thirty-five patients received 105AD7 human anti-idiotype vaccination prior to surgery for colorectal carcinoma. Patients were immunized before and also received one to two immunizations after surgical resection of their colorectal cancer. The vaccine was well tolerated with no associated toxicity. Lymphocytic infiltration within the resected tumors was quantified by immunohistochemistry and image analysis. Enhanced infiltration of helper T cells (CD4) and natural killer (NK) cells (CD56) were observed in the tumors from immunized patients when compared with tumors from stage, grade, site, age, and sex matched unimmunized patients. NK activity was increased in the blood, peaking 7-10 days post immunization and then dropping rapidly and correlating with NK extravasation within the tumor. Comparison of the amino acid sequences of 105AD7 anti-idiotype and the antigen it mimics, CD55, has predicted that patients with HLA-DR1, HLA-DR3, and HLA-DR7 haplotypes should show helper T cell responses following 105AD7 vaccination. Eighty-three percent of patients expressing these haplotypes responded to 105AD7, whereas 88% of patients who failed to express these haplotypes were nonresponders. With a median follow-up of 4 years (range, 2.5-6 years) 65% of patients remained disease free. This trial shows that 105AD7 stimulates antitumor inflammatory responses allowing extravasation within tumor deposits of both helper T cells and NK cells. This represents a way of evaluating immune responses in patients both within the blood and at the tumor site. The study confirms that immunization with a human anti-idiotypic antibody results in immune responses in 83% of patients with a permissive haplotype.

Structural insights into the mechanism of intramolecular proteolysis

A variety of proteins, including glycosylasparaginase, have recently been found to activate functions by self-catalyzed peptide bond rearrangements from single-chain precursors. Here we present the 1.9 A crystal structures of glycosylasparaginase precursors that are able to autoproteolyze via an N --> O acyl shift. Several conserved residues are aligned around the scissile peptide bond that is in a highly strained trans peptide bond configuration. The structure illustrates how a nucleophilic side chain may attack the scissile peptide bond at the immediate upstream backbone carbonyl and provides an understanding of the structural basis for peptide bond cleavage via an N --> O or N --> S acyl shift that is used by various groups of intramolecular autoprocessing proteins.

An orientation anisotropy in the effects of scaling vertical disparities

Gårding et al. (Vis Res 1995;35:703-722) proposed a two-stage theory of stereopsis. The first uses horizontal disparities for relief computations after they have been subjected to a process called disparity correction that utilises vertical disparities. The second stage, termed disparity normalisation, is concerned with computing metric representations from the output of stage one. It uses vertical disparities to a much lesser extent, if at all, for small field stimuli. We report two psychophysical experiments that tested whether human vision implements this two-stage theory. They tested the prediction that scaling vertical disparities to simulate different viewing distances to the fixation point should affect the perceived amplitudes of vertically but not horizontally oriented ridges. The first used elliptical half-cylinders and the 'apparently circular cylinder' judgement task of Johnston (Vis Res 1991;31:1351-1360). The second experiment used parabolic ridges and the amplitude judgement task of Buckley and Frisby (Vis Res 1993;33:919-934). Both studies broadly confirmed the anisotropy prediction by finding that large scalings of vertical disparities simulating near distances had a strong effect on the perceived amplitudes of the vertically oriented stimuli but little effect on the horizontal ones. When distances > 25 cm were simulated there were no significant differential effects and various methodological reasons are offered for this departure from expectations.

Robust and optimal use of information in stereo vision

Differences between the left and right eye's views of the world carry information about three-dimensional scene structure and about the position of the eyes in the head. The contemporary Bayesian approach to perception implies that human performance in using this source of eye-position information can be analysed most usefully by comparison with the performance of a statistically optimal observer. Here we argue that the comparison observer should also be statistically robust, and we find that this requirement leads to qualitatively new behaviours. For example, when presented with a class of stereoscopic stimuli containing inconsistent information about eccentricity of gaze, estimates of this gaze parameter recorded from one robust ideal observer bifurcate at a critical value of stimulus inconsistency. We report an experiment in which human observers also show this phenomenon and we use the experimentally determined critical value to estimate the vertical acuity of the visual system. The Bayesian analysis also provides a highly reliable and biologically plausible algorithm that can recover eye positions even before the classic stereo-correspondence problem is solved, that is, before deciding which features in the left and right images are to be matched.

5,5-trans lactone-containing inhibitors of serine proteases: identification of a novel, acylating thrombin inhibitor

Synthesis of a variety of 5,5-trans fused lactones, related to compounds found in extracts of Lantana camara, has provided a series of novel acylating inhibitors of human thrombin, trypsin, chymotrypsin and human leucocyte elastase. The most effective thrombin inhibitor is 7 with an IC50 of 130 nM and a Kobs/[1] of 4,000 M-1 s-1.

Preoperative carcinoembryonic antigen is related to tumour stage and long-term survival in colorectal cancer

Evidence as to the value of preoperative carcinoembryonic antigen (CEA) in guiding treatment for patients with colorectal cancer is conflicting. The aim of this prospective study was to investigate the value of preoperative CEA in predicting tumour factors of proven prognostic value and long-term survival in patients undergoing surgery for colorectal cancer. Preoperative serum CEA, tumour ploidy, stage and grade were ascertained in 277 patients undergoing colorectal cancer surgery. This cohort of patients were followed up for a minimum of 5 years, or until death, in a dedicated colorectal clinic. Patients with an elevated CEA had a 5 year survival of 39%. This increased to 57% if the CEA was normal (P=0.001). The proportion of patients with a raised CEA increased with a more advanced tumour stage (P < 0.000001) and a poorly differentiated tumour grade (P < 0.005). Once stage had been controlled for, CEA was not a predictor of survival. No relationship between tumour ploidy and CEA was found. In conclusion, a raised preoperative serum CEA is likely to be associated with advanced tumour stage and poor long-term survival, compared with patients with a normal value.

Pertussis encephalopathy with high cerebrospinal fluid antibody titers to pertussis toxin and filamentous hemagglutinin

A 7-year-old unimmunized girl with pertussis presented with respiratory failure and electroencephalographic evidence of an encephalopathy. The cerebrospinal fluid (CSF)/serum ratio of antibodies to pertussis toxin and filamentous hemagglutinin were 11- and ninefold higher than the CSF/serum ratio of total immunoglobulin G. The CSF/serum ratio of albumin was normal. These findings indicate production of antibodies in the central nervous system to Bordetella pertussis antigens and imply, therefore, that the pertussis encephalopathy in this girl was associated with the entry of pertussis antigens into the central nervous system.

Vergence control across saccades in dyslexic adults

Many aspects of vision have been investigated in developmental dyslexia. Some research suggests deficits in vergence control (e.g. Buzzelli, 1991, Optom. Vision Sci. 68, 842-846), although ability to control vergence across saccades has not yet been investigated. We have explored this question indirectly using Enright's (1996 Vision Res. 36, 307-312.) sequential stereopsis task. The task requires observers to set two adjacent targets (whose textures cannot be resolved simultaneously if either is fixated) to appear equi-distant. Enright has argued that sequential stereopsis stereoacuity thresholds offer an indication of vergence control across saccades. We report two experiments using a total of 17 dyslexic and 18 control adults. Performance was measured on a sequential stereopsis task and an ordinary 'simultaneous' stereopsis task. No significant differences between groups were found. However, whereas practice of the sequential task lowered control group thresholds on the simultaneous task, for the dyslexic group it significantly raised thresholds, suggesting that visual fatigue is especially important in investigations of visual functions in dyslexia. Although the small samples used limit conclusions at this stage, the main sequential stereopsis results suggest that, if Enright is correct, dyslexic adults can show normal vergence control across saccades.

Serum from preeclamptic women induces vascular cell adhesion molecule-1 expression on human endothelial cells in vitro: a possible role of increased circulating levels of free fatty acids

OBJECTIVE

The object was to determine whether serum from preeclamptic women induces expression of vascular cell adhesion molecule-1 on cultured endothelial cells.

STUDY DESIGN

Endothelial cells were incubated with medium containing 20% serum (volume/volume) either from women with preeclampsia (n = 15) or from women with normal pregnancies (n = 15) matched for maternal age, gestational age, and parity. A further matched set of samples (n = 10) was exposed to endothelial cells that had previously been incubated in the presence or absence of vitamin E (40 micromol/L final concentration). Free fatty acids were determined in each sample. A mixture of free fatty acids (linoleic, oleic, and palmitic acids, 1:1:1) was added to serum from control subjects in increasing concentrations (70-280 micromol/L final concentration) to emulate preeclamptic serum and the preparation was exposed to endothelial cells. In each experiment vascular cell adhesion molecule-1 expression was determined after 16 hours of exposure by an enzyme-linked immunosorbent assay technique performed on the cell monolayer.

RESULTS

Preeclamptic serum had higher levels of free fatty acids than did that of control subjects (0.71 mmol/L, 95% confidence level 0.5-0.93, vs 0.36 mmol/L, 95% confidence level 0.28-0.43). There was a statistically significant increase in vascular cell adhesion molecule-1 expression on the endothelial cells exposed to preeclamptic serum compared with those exposed to control serum (optical density 0.17 vs 0.11). Vitamin E reduced the vascular cell adhesion molecule-1 expression of endothelial cells exposed both to preeclamptic and to control serum samples in a nonspecific manner. Addition of free fatty acids to normal pregnancy serum to mimic the effect of preeclampsia resulted in increased expression of vascular cell adhesion molecule-1 on the cells.

CONCLUSION

Preeclamptic serum induces vascular cell adhesion molecule-1 expression on human endothelial cells in vitro, an effect also produced by fatty acids. The elevated level of free fatty acids in women with preeclampsia may contribute to increased vascular cell adhesion molecule expression in vivo.

Crystal structures of Flavobacterium glycosylasparaginase. An N-terminal nucleophile hydrolase activated by intramolecular proteolysis

Glycosylasparaginase (GA) is a member of a novel family of N-terminal nucleophile hydrolases that catalytically use an N-terminal residue as both a polarizing base and a nucleophile. These enzymes are activated from a single chain precursor by intramolecular autoproteolysis to yield the N-terminal nucleophile. A deficiency of GA results in the human genetic disorder known as aspartylglycosaminuria. In this study, we report the crystal structure of recombinant GA from Flavobacterium meningosepticum. Similar to the human structure, the bacterial GA forms an alphabetabetaalpha sandwich. However, some significant differences are observed between the Flavobacterium and human structures. The active site of Flavobacterium glycosylasparaginase is in an open conformation when compared with the human structure. We also describe the structure of a mutant wherein the N-terminal nucleophile Thr152 is substituted by a cysteine. In the bacterial GA crystals, we observe a heterotetrameric structure similar to that found in the human structure, as well as that observed in solution for eukaryotic glycosylasparaginases. The results confirm the suitability of the bacterial enzyme as a model to study the consequences of mutations in aspartylglycosaminuria patients. They also suggest that further studies are necessary to understand the detail mechanism of this enzyme. The presence of the heterotetrameric structure in the crystals is significant because dimerization of precursors has been suggested in the human enzyme to be a prerequisite to trigger autoproteolysis.

Sequential stereopsis using high-pass spatial frequency filtered textures

Enright [(1995). Perception, 24 (suppl.), 32-33; (1996). Vision Research, 36, 307-312] described a simple piece of equipment for demonstrating a perceptual mechanism he called sequential stereopsis. The equipment requires an observer to set two textured targets seen behind a pair of small viewing ports to appear equi-distant. The principle upon which the apparatus depends is the use of textures whose elements cannot be resolved in peripheral vision at the eccentricity determined by the target separation. Enright used a fine sandpaper for this purpose. We have conducted two similar experiments using high bandpass filtered textures which eliminate any possibility that the low spatial frequency content of sandpaper textures could play a role. Our results corroborate Enright's general conclusions on sequential stereopsis, while at the same time showing that high-pass textures do not give wholly similar results to sandpaper.

Sequential Stereopsis Demonstrated with High-Bandpass Spatial-Frequency Filtered Textures

Enright (1995 Vision Research36 307 – 312; 1995 Perception24 Supplement, 32 – 33) described a simple piece of equipment for demonstrating a highly sensitive perceptual mechanism that he called sequential stereopsis. The apparatus prevents ‘conventional’ stereopsis mechanisms from operating as it prevents the comparisons of disparities of targets seen at the same time. Enright suggested that the mechanism of sequential stereopsis relies on a comparison of disparities before and after isovergent saccades between fixations of the two targets. In his apparatus, the observer makes fixations between two textured targets seen behind a pair of viewing ports and the task is to adjust these to appear equidistant. The principle upon which the apparatus depends is the use of textures whose elements cannot be resolved in peripheral vision at the eccentricity determined by the target separation. Enright used a fine sandpaper for this purpose. We describe two similar experiments ( N=3 in both) with high-bandpass filtered textures which eliminate any possibility of the low-spatial-frequency content of sandpaper textures playing a role. Our results corroborate Enright's general conclusions on sequential stereopsis while at the same time showing that high-bandpass textures do not give wholly similar results to sandpaper. Possible reasons for this are discussed.

Unusual manifestations of type 1 autoimmune polyendocrinopathy

We present a family with five members affected by Type 1 autoimmune polyendocrinopathy. All patients had chronic mucocutaneous candidiasis and dental abnormalities. Four patients had ocular abnormalities, four had hypoparathyroidism, and three had Addison's disease. The family was unusual in that all four affected females had premature ovarian failure. The ocular abnormalities included two patients with subcapsular lens opacities, one patient with asymptomatic corneal opacities, and one patient with severe bilateral iridocyclitis with cataract formation. One patient had pernicious anaemia and one had insulin dependent diabetes mellitus. All patients were negative on repeated occasions for organ specific and non-organ specific autoantibodies. Lymphocyte studies were performed in four patients. A deficiency of T suppressor cells was found in three and low normal levels were present in the fourth suggesting that the syndrome may be due to a defect in suppressor T cells.