Bacterial endocarditis due to Haemophilus parainfluenzae

We have evaluated three patients with Haemophilus parainfluenzae endocarditis. Two of the three had underlying heart disease. All presented with fever, chills and malaise of less than two weeks' duration. Mitral valve involvement led to congestive heart failure in two of three cases. Treatment proved difficult, despite normally adequate dosages of antibiotics to which the pathogens were sensitive in vitro (ampicillin, 12-20 gm/dag; gentamicin, 3-5 mg/kg/day). Two patients were cured; one died. There was a suggestion of an inverse correlation between vegetation mass and favorable clinical response. Review of the English literature disclosed 22 documented cases of H parainfluenzae endocarditis, including 12 in the antibiotic era.     

Visual receptive-field properties of single neurons in cat's ventral lateral geniculate nucleus

1. Visual receptive-field characteristics were determined for 154 cells in the ventral lateral geniculate nucleus (VLG) of cats anesthetized with nitrous oxide. All cells were verified histologically to be within the VLG. Responses of 182 cells from laminae A and A1 of the dorsal lateral geniculate nucleus (DLG) were tested for comparison. 2. The VLG cells could be grouped into one of seven classes according to their responses to light stimulation. Twenty-seven percent of the cells had uniform receptive fields. They responded maximally to stationary stimuli flashed on or off anywhere within the receptive field and showed no evidence for antagonistic surround mechanisms. About 19.5% of the VLG cells had concentric receptive fields. They were similar to the uniform type, with the addition of a concentric inhibitory surround. Eight percent of the VLG cells had ambient receptive fields. These cells were characterized by an unusually regular maintained discharge which varied in rate in relation to the level of receptive-field illumination or of full-field ambient illumination. About 4% of the VLG cells were movement sensitive. They gave little or no response to stationary stimuli flashed on or off in the receptive field, and responded best to a contour moving across the receptive field in any direction. An additional 2.5% of the VLG cells were direction sensitive. Their response was dependent on the direction of stimulus movement through the receptive field. Sixteen percent of the VLG cells had indefinite receptive fields. They responded to whole-eye illumination or to localized visual-field stimulation; however, specific receptive-field properties could not be adequately defined. Approximately 23% of the VLG cells studied gave no convincing response to visual stimulation. 3. Responses of DLG cells agreed with those reported in previous studies. Almost all (97%) had concentric receptive fields, and a few (3%) had uniform receptive fields with no apparent antagonistic surround. None of the DLG cells had receptive fields like those in the other classes found for VLG cells. 4. The VLG cells tended to have large receptive fields; mean diameter was 10.6 degrees of visual arc. This was substantially larger than the diameter of receptive fields for DLG cells. In addition, VLG cells generally required larger stimuli than DLG cells to respond. There was no consistent relationship between receptive-field size and visual-field eccentricity for VLG cells, in contrast to the DLG. Most (57%) VLG cells were driven only by the contralateral eye, 30% were binocularly driven, and 13% were driven only by the ipsilateral eye. 5. A systematic visuotopic organization was present in the VLG. The lower visual field was represented anteriorly in the nucleus and the upper visual field posteriorly. The vertical meridian was represented along the dorsomedial border of the VLG where it abuts the DLG, and the temporal periphery was represented ventrolaterally. 6. Responses to electrical stimulation of the optic chiasm were studied for 55 VLG cells...