Journey to the center of the category: the dissociation in amnesia between categorization and recognition.

The authors' theoretical analysis of the dissociation in amnesia between categorization and recognition suggests these conclusions: (a) Comparing to-be-categorized items to a category center or prototype produces strong prototype advantages and steep typicality gradients, whereas comparing to-be-categorized items to the training exemplars that surround the prototype produces weak prototype advantages and flat typicality gradients; (b) participants often show the former pattern, suggesting their use of prototypes; (c) exemplar models account poorly for these categorization data, but prototype models account well for them; and (d) the recognition data suggest that controls use a single-comparison exemplar-memorization process more powerfully than amnesics. By pairing categorization based in prototypes with recognition based in exemplar memorization, the authors support and extend other recent accounts of cognitive performance that intermix prototypes and exemplars, and the authors reinforce traditional interpretations of the categorization-recognition dissociation in amnesia.

Prototypes in category learning: the effects of category size, category structure, and stimulus complexity.

Although research in categorization has sometimes been motivated by prototype theory, recent studies have favored exemplar theory. However, some of these studies focused on small, poorly differentiated categories composed of simple, 4-dimensional stimuli. Some analyzed the aggregate data of entire groups. Some compared powerful multiplicative exemplar models to less powerful additive prototype models. Here, comparable prototype and exemplar models were fit to individual-participant data in 4 experiments that sampled category sets varying in size, level of category structure, and stimulus complexity (dimensionality). The prototype model always fit the observed data better than the exemplar model did. Prototype-based processes seemed especially relevant when participants learned categories that were larger or contained more complex stimuli.

Demonstration of varicella-zoster virus infection in the muscularis propria and myenteric plexi of the colon in an HIV-positive patient with herpes zoster and small bowel pseudo-obstruction (Ogilvie's syndrome).

Gastrointestinal symptomatology as a complication of herpes zoster (HZ) is extremely rare, with the majority of reported cases showing only temporal or radiological evidence of GI tract involvement by varicella zoster virus (VZV) infection. We present the first case of documented direct VZV infection in the muscularis propria of the gut presenting as intestinal pseudo-obstruction (Ogilvie's syndrome). The patient was a 34-yr-old HIV+ man who developed small bowel pseudo-obstruction in association with disseminated cutaneous HZ. A partial ileocolectomy specimen demonstrated a focal ulcer in the terminal ileum. Immunohistochemistry against VZV gpI demonstrated diffuse staining of the muscularis propria and myenteric plexi throughout the length of the specimen. Viral particles consistent with Herpesviridae were shown to be present ultrastructurally. We postulate that the viral infection in the neuronal plexi and muscularis propria caused muscle injury leading to pseudo-obstruction.

Thirty categorization results in search of a model.

One category structure dominated in the shift toward exemplar-based theories of categorization. Given the theoretical burden on this category structure, the authors reanalyzed 30 of its uses over 20 years in 8 articles. The authors suggest 4 conclusions. (a) This category structure may encourage exemplar-memorization processes because of its poor structure, the learning difficulties it causes, and its small, memorizable exemplar sets. Its results may only generalize narrowly. (b) Exemplar models have an advantage in fitting these 30 data sets only because they reproduce a performance advantage for training items. Other models fit equally well if granted this capacity. (c) A simpler exemplar process than assumed by exemplar models suffices to explain these data sets. (d) An important qualitative result predicted by exemplar theory is not found overall and possibly should not even be expected. The authors conclude that the data produced by this category structure do not clearly support exemplar theory.

Aluminum silicate-containing psammoma bodies in a cervicovaginal smear (Pap): cytological, ultrastructural, and radiographic microprobe studies.

Psammoma body is a rare finding in a cervicovaginal smear and can be associated with either benign or malignant diseases. Here we report a case to illustrate the association of psammoma bodies with benign granulomatous reactions to a foreign material (aluminum silicate).

Desmin myopathy involving cardiac, skeletal, and vascular smooth muscle: report of a case with immunoelectron microscopy.

Desmin myopathy is a rare idiopathic disorder characterized by abnormal aggregates of desmin-type intermediate filaments, which affects cardiac and skeletal muscle, and rarely the intestinal smooth muscle. We report a 42-year-old woman with atrial fibrillation and progressive restrictive cardiomyopathy. Left ventricular biopsy, cardiac explant, and subsequent autopsy study of skeletal muscle revealed cytoplasmic granulo-filamentous inclusions that were continuous with Z-lines and were immunoreactive for desmin filaments both at the light immunohistochemical and electron microscopic level. In addition, we report the presence of characteristic inclusions within the smooth muscle of intramural coronary blood vessels. This is the first description of desmin inclusions within vascular smooth muscle, and underscores the systemic nature of this rare myopathy.

Massive macrophage lipid accumulation presenting as hepatosplenomegaly and lymphadenopathy associated with long-term total parenteral nutrition therapy for short bowel syndrome.

We present a unique case of massive splenomegaly, hepatomegaly, and lymphadenopathy caused by lipid-laden macrophages in a 50 year old white female with short-bowel syndrome treated with long-term total parenteral nutrition. Using transmission electron microscopy and special stains we were able to show that the total parenteral nutrition lipid component was composed of lipid droplets and micelles morphologically identical to those found in lipid-laden macrophages which had accumulated in the patient's reticuloendothelial system leading to massive splenomegaly, hepatomegaly (without evidence of steatosis) and lymphadenopathy. While this phenomenon has been reported in animal models, no human cases have been previously reported.

Whipple's disease involving the mesenteric lymph nodes diagnosed by fine-needle aspiration.

Although it traditionally presents with signs and symptoms of small intestine involvement, such as diarrhea and malabsorption, Whipple's disease (WD) can involve many other organs. Typically, WD diagnosis is established by biopsy of the small intestine. A case of WD, established by duodenal biopsy, in a 36-yr-old male is presented. This patient developed mesenteric lymphadenopathy, prompting computerized-tomography guided fine-needle aspiration (FNA), which showed typical features of WD. Electron microscopy (EM) studies confirmed the diagnosis. To our knowledge, this is the first reported case of lymph-node involvement in WD diagnosed by FNA biopsy.

Prolonged storage of tissues at low temperatures does not preclude their use for ultrastructural studies.

A cost-effective method for electron microscopic study of snap-frozen surgical specimens is described. The method is available to any surgical pathology laboratory equipped with a deep freezer and allows the performance of ultrastructural observations on archival material.

Acrylic resin pneumoconiosis: report of a case in a dental student.

Pneumoconiosis in dental laboratory workers has been associated with exposure to metal alloys and silica used in the manufacturing of dental prosthetics. In this report, we describe a 27-yr-old dental student who was found to have bilateral basal pulmonary interstitial infiltrates and nodules on a chest roentgenogram after a brief episode of upper respiratory infection. An open lung biopsy revealed interstitial pneumonitis with an abundance of vacuolated macrophages in the alveolar spaces. Ultrastructural analysis showed in the alveolar and interstitial spaces the accumulation of macrophages laden with electron-lucent bodies resembling plastic beads. An inhalation exposure history, taken subsequent to these findings, revealed exposure to high levels of acrylic plastic in a dental school laboratory. Removal from the site of exposure has resulted in the gradual resolution of the roentgenographic abnormalities.

Collagen matrix influences the morphologic features and steroid secretion of human granulosa cells.

Steroid secretion and structure of granulosa cells on floating collagen gels were compared with those of cells grown on plastic. Granulosa cells from follicles of gonadotropin-treated women were plated either onto dishes coated with type I collagen or onto plastic dishes. Medium containing serum was removed after 24 hours, defined medium was added, and the gel was floated. Medium was changed daily for 3 days, after which the granulosa cells were prepared for light and electron microscopy. Cells grown on collagen secreted significantly more estradiol and progesterone than those grown on plastic during the 3 days of culture. The round multilayered granulosa cells on collagen had abundant mitochondria and lipid droplets and they formed numerous intercellular junctions. On plastic surfaces, flat granulosa cells grew as a monolayer with few junctions and less abundant mitochondria or lipid droplets. We conclude that growth on floating collagen promotes structural changes of human granulosa cells that enhances cell interaction and secretion of steroid hormones.