Comparison of Snellen letter and Vistech grating charts as refraction targets

Snellen letter and Vistech sine wave grating charts were used as refraction targets to determine differences in times required to accomplish subjective refractions, endpoint refractive values, and subject preferences. Thirty hyperopes and 30 myopes, divided into three age groups, were selected as subjects. Two examiners tested each subject using each chart. Both timed their subjective refractions and recorded their findings. After all data were recorded, each subject completed a questionnaire to determine chart preference. There were no clinically significant mean differences between the charts in terms of endpoint refractive data, but, on average, the Snellen chart was faster to use. Chart rating depended on the subject's refractive status with more myopes preferring the Snellen chart and more hyperopes rating the grating chart higher.     

Mental object rotation in Parkinson's disease.

Deficits in visual-spatial ability can be associated with Parkinson's disease (PD), and there are several possible reasons for these deficits. Dysfunction in frontal-striatal and/or frontal-parietal systems, associated with dopamine deficiency, might disrupt cognitive processes either supporting (e.g., working memory) or subserving visual-spatial computations. The goal of this study was to assess visual-spatial orientation ability in individuals with PD using the Mental Rotations Test (MRT), along with other measures of cognitive function. Non-demented men with PD were significantly less accurate on this test than matched control men. In contrast, women with PD performed similarly to matched control women, but both groups of women did not perform much better than chance. Further, mental rotation accuracy in men correlated with their executive skills involving mental processing and psychomotor speed. In women with PD, however, mental rotation accuracy correlated negatively with verbal memory, indicating that higher mental rotation performance was associated with lower ability in verbal memory. These results indicate that PD is associated with visual-spatial orientation deficits in men. Women with PD and control women both performed poorly on the MRT, possibly reflecting a floor effect. Although men and women with PD appear to engage different cognitive processes in this task, the reason for the sex difference remains to be elucidated.     

Clenched-fist injury complicated by methicillin-resistant Staphylococcus aureus

Hand infections are a common sequela of clenched-fist injuries. The majority of these infections are due to Staphylococcus and Streptococcus species. Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being isolated in Canadian health care facilities. In addition, MRSA now needs to be considered in community acquired hand infections that fail to respond to common empiric therapy. A 51-year-old man with MRSA due to a hand injury was treated successfully with vancomycin. The prevalence, mechanism of resistance and treatment of MRSA are briefly reviewed.     

Morphology of retinal ganglion cells in lungless salamanders (fam. Plethodontidae): an HRP and Golgi study

The family Plethodontidae consists of nearly two-thirds of all living urodeles; most of them possess highly developed visual abilities. We investigated the morphology of retinal ganglion cells (RGCs) in four representative species by means of the horseradish peroxidase method in flatmounts and in transverse sections and with the Golgi method in transverse sections. In flatmount preparations, four classes of RGCs were found, differing in dendritic arborization, dendritic field size, and stratification pattern of dendrites in the inner plexiform layer (IPL). Class-1 cells had small dendritic fields (29-44 microns 2) and arborized throughout the entire depth of the IPL. Class-2 cells had medium to large dendritic fields (75-206 microns 2) and mostly arborized in two or three laminae or in a diffuse fashion in the IPL. Class-3 cells had medium to large dendritic fields (72-200 microns 2) but sparse dendritic arborization. They only arborized in the proximal lamina of the IPL. Class-4 cells had large dendritic fields (273-626 microns 2) and branched in the most sclerad stratum of the IPL. No large differences in intraspecific soma size of the different RGC classes were detected (although interspecific soma size varied to a considerable degree) and no "giant" cells typically found in other vertebrate retinas were present. The results suggest that, with respect to the pattern of arborization and stratification of dendrites, lungless salamanders possess morphological classes of RGC similar to those found in frogs, but the morphology of RGCs in lungless salamanders seems to be simplified in comparison to frog RGCs. This simplification might be a consequence of paedomorphosis.     

Examination of central vision. Visual acuity, contrast sensitivity, color vision

In the neurophysiological organization of the visual system, form, color, movement, and depth perception are processed separately. Therefore, sensorial examination methods should test each of these basic functions separately, since they may be affected individually or to different extents by pathologic processes. For diagnosis the limit of visual acuity, i.e., the capacity for discrimination must be searched for, using Paliaga's "limits method". Visual acuity can also be tested in infants by the preferential looking method. Contrast sensitivity is tested using sinusoidal grid patterns of varying contrast and spatial frequency. In routine practice, however, this is usually achieved more easily with acuity cards on which contrast is reduced in several stages. The "two-equation method" is a colorimetric test combining two metameric matches, red + green = yellow, and blue + green = cyan, for testing color vision. The test requires an anomaloscope or anomalometer with four light channels. With this method it is possible to test the "red", "green", and "blue" cones and the "red-green" and "blue-yellow" opponents. The test provides a qualitative and quantitative evaluation of color vision disorders. If no colorimeter is available, classic printed test can be used. However, they might never achieve the same qualitative and quantitative precision.     

Einige Befunde zur Sinnesphysiologie der Kaltblüterzecke Amblyomma testudinis

Zusammenfassung Aus eigener Zucht stammende Larven, Nymphen und Imagines von Amblyomma testudinis wurden auf ihre Sinnesleistungen hinsichtlich Phototaxis, Thermotaxis, Geotaxis und Chemotaxis untersucht. Es ergab sich ein entwicklungsabhängiger Wandel im phototaktischen Verhalten von anfangs positiver Phototaxis bei den Larven über indifferente Phototaxis bei vollgesogenen Larven und nüchternen Nymphen zu negativer Phototaxis bei vollgesogenen Nympen sowie - und -Imagines. Sämtliche Entwicklungsstadien mit Ausnahme der -Imagines verhalten sich temperaturindifferent vor dem Kontakt mit einem Wirt; vollgesogene Larven und Nymphen dagegen bevorzugen niedrige Temperaturen. Nymphen und Imagines, die noch nicht gesogen haben, reagieren negativ geotaktisch. Sie erklettern vermutlich in der Natur die Spitzen von Pflanzen und Steinen, um dort das Vorbeikriechen eines Wirtes abzuwarten. Imagines von Amblyomma testudinis reagieren mit einer positiven Chemotaxis auf Schlangen stärker als auf Kröten. Auch Substrat aus Schlangenbehältern enthält mindestens für 30 Std nach der Entfernung der Schlangen chemotaktisch wirksame Stoffe.

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Contributions to sensory physiology of the tick Amblyomma testudinis

Summary Phototaxis, thermotaxis, geotaxis and chemotaxis of larvae, nymphs and adults of Amblyomma testudinis from own breedings were studied. The phototactic behaviour changed according to the different stages of development: unfed larvae were positively phototactic, fed larvae and unfed nymphs were indifferent, fed nymphs but also the adults showed a negative phototaxis.—All stages of development besides the females reacted without any preference for a distinct temperature, whereas larvae and nymphs after feeding prefered lower temperatures.—Unfed nymphs and adults were negatively geotactic which corresponds to their natural behaviour of climbing plants for catching hosts.—Adults of Amblyomma testudinis showed a higher rate of chemotaxis for snakes than for toads; substrate from snake cages containes chemotaxis inducing substances for more than 30 hours after elimination of the snakes.

     

Sickle cell disease in Sicily.

The chemical and physical properties of haemoglobin S derived from homozygotes for this haemoglobin in Sicily were examined, as well as some erythrocytic characteristics. Sicilian Hb S was identical to that found in USA black patients in electrophoretic mobility on both starch and citrate agar media, solubility, mechanical precipitation rate of oxyhaemoglobins, and minimum gelling concentration, as well as by peptide mapping and amino-acid analysis of all beta-chain peptides. Taken together with the presence in Sicily of African blood group markers and certain historical considerations, it seems clear that the source of Hb S in Sicily is Africa. While the clinical severity in nine Sicilian children did not seem remarkably different from the disease in the USA, the most severe and fatal complications were not seen. Mean Hb F Was 10.5% and 2,3-diphosphoglycerate (2,3-DPG) values were higher in Sicilian homozygotes than in black USA counterparts (21.79 mumol/g Hb vs 15.16). Red cell AT values were also slightly higher in Sicilian patients. The presence of concomitant thalassaemia was excluded by both family studies and globin chain synthetic ratios. In conclusion, haemoglobin S in Sicilian homozygotes is identical to Hb S found in USA blacks. Although the severity of the disease seems quite similar in both groups of patients, other erythrocytic properties were found to be different. Whether these factors influence severity remains to be elucidated.     

A Novel Application of the MIRC Repository in Medical Education

Medical students on the radiology elective in our institution create electronic presentations to present to each other as part of the requirements for the rotation. Access was given to previous students presentations via the web-based system, Medical Imaging Resource Center (MIRC) project, created and supported by the Radiological Society of North America (RSNA). RadPix Power 2 MIRC (Weadock Software, LLC, Ann Arbor, MI) software converted the Microsoft PowerPoint (Redmond, WA) presentations to a MIRC-compatible format. The textual information on each slide is searchable across the entire MIRC database. Future students will be able to benefit from the work of their predecessors.