Sequential ideal-observer analysis of visual discriminations.

Visual stimuli contain a limited amount of information that could potentially be used to perform a given visual task. At successive stages of visual processing, some of this information is lost and some is transmitted to higher stages. This article describes a new analysis, based on the concept of the ideal observer in signal detection theory, that allows one to trace the flow of discrimination information through the initial physiological stages of visual processing, for arbitrary spatio-chromatic stimuli. This ideal-observer analysis provides a rigorous means of measuring the information content of visual stimuli and of assessing the contribution of specific physiological mechanisms to discrimination performance. Here, the analysis is developed for the physiological mechanisms up to the level of the photoreceptor. It is shown that many psychophysical phenomena previously attributed to neural mechanisms may be explained by variations in the information content of the stimuli and by preneural mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cellular proliferation characteristics of basal cell carcinoma: relationship to clinical subtype and histopathology

The authors conducted a retrospective study of 80 cases of pressure sores of the pelvic girdle. This study was designed to evaluate the therapeutic approach, surgical reconstruction techniques and their results at 1 year. Only 32 patients (40%) underwent surgical reconstruction, always using regional pedicled myocutaneous flaps. 15.6% of these patients developed a local recurrence (5/32). Analysis of the results of this series shows that failures of reconstruction cannot be attributed to surgical techniques, but to their indications. The reduction of recurrences depends on earlier medical and surgical management and more rigorous patient selection, especially concerning psychological aspects. The patient's cooperation is an essential condition to the success of treatment.     

Brachytherapy and breast cancer

The study compares, in true adenocarcinoma of the cardia and in adenocarcinoma in Barrett's esophagus, the prevalence of early cancers and their outcome in those patients suitable for resection surgery. From 1980 to 1993, 26 of 350 (7.4%) resected adenocarcinomas of the esophago-gastric junction were pathologically staged as early cancer or pT1. The prevalence of early cancer was 3.7% (11/294) for true cancer of the cardia and 27% (15/56) for cancer in Barrett's esophagus (P < 0.001). Ten of the 15 latter cancers were diagnosed during endoscopic surveillance for benign Barrett's esophagus. Among early cancers, there were four mucosal and 22 submucosal tumours; of the latter, eight had lymph node metastasis and seven neoplastic permeation of lympho-hematic vessels. The most frequently used surgical procedure was esophago-gastric resection and gastric pull-up. Postoperative morbidity was 15.4%, and hospital mortality 3.8%. Excluding postoperative deaths, the overall 5-year survival rate was 79% for early cancer of the cardia and 83% for early cancer in Barrett's esophagus (log rank test = 0.0214, P = 0.88). Overall, the survival rate was 100% in the absence of lymph node metastasis and 43% in the presence of node metastasis (log rank test = 15.811, P = 0.0001). Only one of five patients with both node metastasis and vessel infiltration survived longer than 5 years. In conclusion, the prevalence of early cancer was significantly greater for cancer in Barrett's esophagus than for true cancer of the cardia. Prognosis of the two types of tumour after resection surgery was the same and depended on lymph node status and neoplastic permeation of lympho-hematic vessels.     

Toxic megacolon as a complication of Campylobacter jejuni enterocolitis

We report the case of a previously healthy 53-year-old white male who developed an extraordinary complication of acute Campylobacter jejuni colitis. Toxic megacolon occurred while the patient was treated with a fluoroquinolone antibiotic and glucocorticoids, which were given for endoscopically suspected Crohn's colitis. During the course of the disease no cause of colitis was found other than C. jejuni. Despite the extreme dilatation, the patient was treated conservatively with parenteral nutrition and repeated decompression colonoscopies and made a full, though slow, and uneventful recovery. Follow-up colonoscopies for up to 4 years showed persistent scarring of the transverse colon, probably due to the extreme dilatation, and mild unspecific inflammation of the terminal ileum without histological evidence of inflammatory bowel disease. A comparison with the 6 previously published cases leads to the following conclusions: in most cases the transverse colon is most severely affected. Treatment with either antimotility agents or systemic glucocorticoids does not seem to promote colonic dilatation. The complication has affected patients of both sexes (4 women, 3 men), in the age range of 21 to 83 years, most of them without an underlying disease. The interval between the start of diarrhea and development of the megacolon ranged widely from 3 to 33 days, as did recovery time (2 days to several months). Three of the 7 patients underwent colectomy for imminent or actual colonic perforation. The delayed recovery of our patient was partly attributed to colonic damage caused by extreme dilatation, leading to ischaemia and subsequent scarring of the mucosa, which persisted. Histologically no Crohn's disease or ulcerative colitis could be found at any stage. A rapid increase in resistance of C. species against fluoroquinolone antibodies has been observed in recent years, due to use of the antibiotics in farming. Our patient's severe illness may partly have resulted from delayed effective antibiotic treatment due to resistance. Antibiotic resistance to common enteropathogens should be considered in the case of unusually prolonged or severe enterocolitis. The level of suspicion for either infection or inflammatory bowel disease should remain high as it may be impossible to distinguish between them on the basis of clinical or endoscopic criteria alone.     

Otitis media with effusion: a disability or not?

Otitis media with effusion (OME) is a disease most commonly affecting the paediatric population. However, it is a condition that is also seen in adults and does lead to significant morbidity. We studied the effect of surgical treatment of OME in an adult population and found that the subjective relief of symptoms exceeded the objective audiometric gain. In children where subjective symptoms are perhaps more difficult to assess the clinician needs to beware of underestimating the effect of a hearing loss.     

Overview of the preparation, use and biological studies on polyglycerol polyricinoleate (PGPR)

The esterification of condensed castor oil fatty acids with polyglycerol gives a powerful water-in-oil emulsifier which is used by the food industry in tin-greasing emulsions and as an emulsifier with lecithin in chocolate couverture and block chocolate. A safety evaluation programme was undertaken in the late 1950s and early 1960s to determine whether this food emulsifier polyglycerol polyricinoleate (PGPR). (Quest International trade name ADMUL WOL) presented any health implications for consumers. This programme included acute toxicity tests, subacute rat and chicken toxicity studies, a rat chronic toxicity/multigeneration reproduction study, rodent metabolism, carcinogenicity testing in rat and mouse and a human clinical evaluation. PGPR was found to be 98% digested by rats and utilized as a source of energy superior to starch and nearly equivalent to groundnut oil. There was no interference with normal fat metabolism in rats or in the utilization of fat-soluble vitamins. Despite the intimate relationship with fat metabolism, no evidence was found of any adverse effects on such vital processes as growth, reproduction and maintenance of tissue homeostasis. PGPR was not carcinogenic in either 2-year rat or 80-week mouse feeding studies. The human studies showed no adverse effects on tolerance, liver and kidney function, and fat balance at levels up to 10 g/day PGPR. The acceptable daily intake for PGPR which was set by JECFA in 1974 and the EC/SCF in 1979 is 7.5 mg/kg body weight/day. The UK FAC in 1992 estimated that the maximum per capita mean daily intake of PGPR is 2.64 mg/kg body weight/day. It can be concluded that the use of ADMUL WOL brand of PGPR in tin-greasing emulsions or in chocolate couverture does not constitute a human health hazard.     

Relating the primitive hierarchy of the PREMO standard to the standard reference model for intelligent multimedia presentation systems

The need for a suitable classification of media types arises for several reasons when building or comparing multimedia systems. Within an Intelligent Multimedia Presentation Systems (IMMPS), it is necessary to formulate and encode design knowledge for decision making on the appropriate medium in which to present information and for the generation of the presentation. It is also required in order to specify interfaces to and between system components which will be employed to run a generated presentation before the user's eyes. This task is reflected in the Standard Reference Model (SRM, see this volume) for IMMPS by the Presentation Display Layer. However, the SRM does not instantiate this layer in detail, but instead refers to the Presentation Environment for Multimedia Objects (PREMO) ISO/IEC standard which provides a reference model for a presentation runtime environment for multimedia. PREMO already contains a set of basic structures, the so-called PREMO Primitive Hierarchy, to describe different media types. Thus the question arises, as to how far the PREMO Primitive Hierarchy could serve as a media classification for the SRM in general. In particular, this would support consistency between the design and presentation layers of the SRM if PREMO were used to instantiate the presentation layer. In the current paper, we first point to a number of typical problems with generating classifications of media types. We then provide a brief introduction to PREMO and its Primitive Hierarchy. Finally, the benefits and costs of using the PREMO Primitive Hierarchy for the SRM are discussed.