Using color and grayscale images to teach histology to color-deficient medical students

Examination of histologic and histopathologic microscopic sections relies upon differential colors provided by staining techniques, such as hematoxylin and eosin, to delineate normal tissue components and to identify pathologic alterations in these components. Given the prevalence of color deficiency (commonly called "color blindness") in the general population, it is likely that this reliance upon color differentiation poses a significant obstacle for several medical students beginning a course of study that includes examination of histologic slides. In the past, first-year medical students at Michigan State University who identified themselves as color deficient were encouraged to use color transparency overlays or tinted contact lenses to filter out problematic colors. Recently, however, we have offered such students a computer monitor adjusted to grayscale for in-lab work, as well as grayscale copies of color photomicrographs for examination purposes. Grayscale images emphasize the texture of tissues and the contrasts between tissues as the students learn histologic architecture. Using this approach, color-deficient students have quickly learned to compensate for their deficiency by focusing on cell and tissue structure rather than on color variation. Based upon our experience with color-deficient students, we believe that grayscale photomicrographs may also prove instructional for students with normal (trichromatic) color vision, by encouraging them to consider structural characteristics of cells and tissues that may otherwise be overshadowed by stain colors.

Effects of Organizational Support on Potency in Work Teams

This study focuses on team members' perceptions of organizational support as antecedents of team processes and potency. Potency is team members' collective belief that the team can be effective. In a field study of 39 work teams in six organizations, the authors find a positive relationship between organizational support and potency that is mediated by effective team processes. The authors also find a positive relationship between team processes and managers' ratings of team performance that is mediated by potency. Understanding how organizational support affects potency is important because research has consistently found that potency is strongly associated with team performance, yet little is known about how organizational context affects potency. Therefore, this research has practical as well as theoretical implications.

Sarcocystosis of Sarcocystis felis in cats

The features of S. felis sarcocystosis in muscles of the domestic cats (Felis domesticus) were studied. A complete clinical history, post mortem, and histo-pathologic examinations were done for each cat. Multiple protozoan elliptical cysts were in the skeletal muscles, heart, and diaphragm muscles of 3/17 (17.6%) adult cats. Ultrastructural characteristics of the bradyzoites and cyst wall were consistent with those described for S. felis in bobcat and domestic cat. Clinico-pathological study in 3 cats showed hypertrophy cardiomyopathy and lymphosarcoma associated with S. felis. Tissue samples showed a spectrum of pathological changes such as multi-focal subacute myocarditis and multi-focal subarachnoid lymphocytic infiltration. DNA extracted from muscles diaphragm with cysts was tested by PCR and sequence analyses of ssurRNA gene. The phylogenetic reconstructions using neighbor-joining method showed that S. felis is closely related to S. neurona. The results were illustrated and photographed and peer discussed.

Disseminated hemangiosarcoma in the horse: 35 cases

Thirty-five cases of disseminated hemangiosarcoma (21 clinical cases and 14 previously reported cases) were reviewed to describe the disease in horses. Hemangiosarcoma occurred in mature, particularly middle-aged horses, with no apparent sex predilection. Thoroughbreds seemed to be overrepresented (13 cases) but a true breed predilection could not be established. The respiratory and musculoskeletal systems were most commonly affected and presenting complaints included dyspnea (26%), subcutaneous or muscular swelling (24%), epistaxis (17%), and lameness (12%). Heart and respiratory rates were usually increased and mucous membrane color was frequently pale or icteric. Capillary refill time and rectal temperature were often normal. Anemia (88%), neutrophilic leukocytosis (62%), and thrombocytopenia (48%) were common. Examination of tissue samples collected by fine-needle aspirate or biopsy established an antemortem diagnosis in 4 horses. The diagnosis was made during postmortem examination in the remaining 31 horses. The lung and pleura (77%), skeletal muscle (46%), and spleen (43%) were most commonly affected. A primary site of tumor involvement could be identified in 22 horses. Hemangiosarcoma should be included as a differential diagnosis for horses with evidence of hemorrhage into body cavities, skeletal muscle, or subcutaneous locations.

Amylopectinosis in fetal and neonatal Quarter Horses

Three Quarter Horses, a stillborn filly (horse No. 1), a female fetus aborted at approximately 6 months of gestation (horse No. 2), and a 1-month-old colt that had been weak at birth (horse No. 3), had myopathy characterized histologically by large spherical or ovoid inclusions in skeletal and cardiac myofibers. Smaller inclusions were also found in brain and spinal cord and in some cells of all other tissues examined. These inclusions were basophilic, red-purple after staining with periodic acid-Schiff (both before and after digestion with diastase), and moderately dark blue after staining with toluidine blue. The inclusions did not react when stained with Congo red. Staining with iodine ranged from pale blue to black. Their ultrastructural appearance varied from amorphous to somewhat filamentous. On the basis of staining characteristics and diastase resistance, we concluded that these inclusions contained amylopectin. A distinctly different kind of inclusion material was also present in skeletal muscle and tongue of horse Nos. 1 and 3. These inclusions were crystalline with a sharply defined ultrastructural periodicity. The crystals were eosinophilic and very dark blue when stained with toluidine blue but did not stain with iodine. Crystals sometimes occurred freely within the myofibers but more often were encased by deposits of amylopectin. This combination of histologic and ultrastructural features characterizes a previously unreported storage disease in fetal and neonatal Quarter Horses, with findings similar to those of glycogen storage disease type IV. We speculate that a severe inherited loss of glycogen brancher enzyme activity may be responsible for these findings. The relation of amylopectinosis to the death of the foals is unknown.

Coinfection of a bearded dragon, Pogona vitticeps, with adenovirus- and dependovirus-like viruses

Four neonate bearded dragons, Pogona vitticeps, from two collections became ill and died. Multiple tissues were collected and processed for light microscopy. In hematoxylin and eosin-stained sections of liver of one lizard, numerous basophilic intranuclear inclusions were observed. In three lizards, intranuclear inclusions were primarily seen within enterocytes in the small intestine. A portion of paraffin-embedded liver of one lizard and small intestine of a second lizard were removed, deparaffinized, and examined by electron microscopy. For the most part, inclusions in the liver consisted of nonenveloped viral particles 60-66 nm in diameter. Smaller nonenveloped virions 15-17 nm in diameter were occasionally seen in association with these particles. In the intestine, inclusions consisted only of 60-70 nm particles. Based on morphology and location, the larger particles were consistent with an adenovirus. Based on size and presence within nuclei of host cells coinfected with the adenovirus-like virus, the smaller viral agent was consistent with members of the genus Dependovirus.

Rhinosporidiosis: a description of an unprecedented outbreak in captive swans (Cygnus spp.) and a proposal for revision of the ontogenic nomenclature of Rhinosporidium seeberi

Rhinosporidiosis is a mucocutaneous zooanthroponotic disease caused by Rhinosporidium seeberi, a fungal-like organism of uncertain classification with an unknown mode of transmission. Over a 3 year period, 41 captive swans (Cygnus olor and C. atratus) developed conjunctival and cutaneous polypoid lesions diagnosed as rhinosporidiosis by histopathological examination including light and electron microscopy. Investigation of this avian outbreak, the first of its kind, provides additional insight into the epidemiology of this enigmatic aetiologic agent, which has yet to be isolated and cultivated in vitro. The occurrence of rhinosporidiosis in swans supports an aquatic environment as the reservoir for R. seeberi, which is often associated with exposure to water. We report the first known occurrence of rhinosporidiosis in 41 captive mute (C. olor) and Australian black (C. atratus) swans dwelling on a lake in a Central Florida city. Additionally, we review the development stages of R. seeberi and propose a revision in its ontogenic nomenclature to reflect its probable taxonomic classification as a member of the kingdom Fungi.

Adenovirus-associated pneumonia and hepatitis in four llamas

This report focuses on the diagnostic laboratory and necropsy findings in 4 llamas with adenovirus-associated hepatitis or pneumonia. In the 2 young llamas, clinical illness was characterized by chronic respiratory tract disease. In the 2 adult llamas, clinical illness was characterized by neurologic signs and a history of respiratory tract disease. Histologic examination, electron microscopy, virus isolation, and fluorescent antibody results indicated that adenovirus infection was associated with disease in all 4 llamas.

Tuberculosis in five basset hounds

Five Basset Hounds (2 females and 3 males) under the age of 5 years, acquired systemic tuberculosis. We suspected tuberculosis in one dog, because it had histologic lesions similar to those in 4 dogs in which bacteria were identified as Mycobacterium avium complex. A review of canine tuberculosis revealed a similar diagnosis in a Basset Hound. The association of this infection in Basset Hounds suggests an inherited immunologic defect. Results of our survey suggest that the defect might exist in cell-mediated immunity.

Spinal cord medulloepithelioma in a dog

Medulloepithelioma, an embryonal neural tumor, was diagnosed in a 6-month-old Bullmastiff. Clinical signs of incomplete, upper motor neuron, transverse myelopathy involving the hindlimbs were observed on examination. Myelography was required to identify the cause of clinical abnormality. The tumor involved the L1 spinal cord segment.