Using viral metagenomics of brain tissue from a young adult crossbreed steer with acute onset of neurologic disease, we sequenced the complete genome of a novel astrovirus (BoAstV-NeuroS1) that was phylogenetically related to an ovine astrovirus. In a retrospective analysis of 32 cases of bovine encephalitides of unknown etiology, 3 other infected animals were detected by using PCR and in situ hybridization for viral RNA. Viral RNA was restricted to the nervous system and detected in the cytoplasm of affected neurons within the spinal cord, brainstem, and cerebellum. Microscopically, the lesions were of widespread neuronal necrosis, microgliosis, and perivascular cuffing preferentially distributed in gray matter and most severe in the cerebellum and brainstem, with increasing intensity caudally down the spinal cord. These results suggest that infection with BoAstV-NeuroS1 is a potential cause of neurologic disease in cattle.

In studying how environmental factors control the population dynamics of Pfiesteria piscicida Steidinger et Burkholder, we examined the influence of light regime on kleptoplastidic photosynthesis, growth, and grazing. Prey ( Rhodomonas sp.)-saturated growth rate of P. piscicida increased (0.67 Ϯ 0.03 d Ϫ 1 to 0.91 Ϯ 0.11 d Ϫ 1 ) with light intensity varying from 0 to 200 mol photons и m Ϫ 2 и s Ϫ 1 . No significant effect was observed on grazing, excluding the possibility that light enhanced P. piscicida growth through stimulating grazing. Lightgrown P. piscicida exhibited a higher gross growth efficiency (0.78 Ϯ 0.10) than P. piscicida incubated in the dark (0.32 Ϯ 0.16), and photosynthetic inhibitors significantly decreased growth of recently fed populations. These results demonstrate a role of kleptoplastidic photosynthesis in enhancing growth in P. piscicida . However, when the prey alga R . sp. was depleted, light's stimulating effect on P. piscicida growth diminished quickly, coinciding with rapid disappearance of Rhodomonas -derived pigments and RUBISCO from P. piscicida cells. Furthermore, the effect of light on growth was reversed after extended starvation, and starved light-grown P. piscicida declined at a rate significantly greater than dark-incubated cultures. The observed difference in rates of decline appeared to be attributable to light-dependent cannibalism. Using a 5-chloromethylfluorescein diacetate staining technique, cannibalistic grazing was observed after 7 days of starvation, at a rate four times greater under illumination than in the dark. The results from this study suggest that kleptoplastidy enhances growth of P. piscicida only in the presence of algal prey. When prey is absent, P. piscicida populations may become vulnerable to light-stimulated cannibalism.

Validating digital pathology as substitute for conventional microscopy in diagnosis remains a priority to assure effectiveness. Intermodality concordance studies typically focus on achieving the same diagnosis by digital display of whole slide images and conventional microscopy. Assessment of discrete histological features in whole slide images, such as mitotic figures, has not been thoroughly evaluated in diagnostic practice. To further gauge the interchangeability of conventional microscopy with digital display for primary diagnosis, 12 pathologists examined 113 canine naturally occurring mucosal melanomas exhibiting a wide range of mitotic activity. Design reflected diverse diagnostic settings and investigated independent location, interpretation, and enumeration of mitotic figures. Intermodality agreement was assessed employing conventional microscopy (CM40×), and whole slide image specimens scanned at 20× (WSI20×) and at 40× (WSI40×) objective magnifications. An aggregate 1647 mitotic figure count observations were available from conventional microscopy and whole slide images for comparison. The intraobserver concordance rate of paired observations was 0.785 to 0.801; interobserver rate was 0.784 to 0.794. Correlation coefficients between the 2 digital modes, and as compared to conventional microscopy, were similar and suggest noninferiority among modalities, including whole slide image acquired at lower 20× resolution. As mitotic figure counts serve for prognostic grading of several tumor types, including melanoma, 6 of 8 pathologists retrospectively predicted survival prognosis using whole slide images, compared to 9 of 10 by conventional microscopy, a first evaluation of whole slide image for mitotic figure prognostic grading. This study demonstrated agreement of replicate reads obtained across conventional microscopy and whole slide images. Hence, quantifying mitotic figures served as surrogate histological feature with which to further credential the interchangeability of whole slide images for primary diagnosis.

No abstract