Biomedical subjects

N Tumosa

Publications and source records attributed to N Tumosa.

23 records · Page 2Linked to original sources

PubMed1982

Visual field deficits in cats reared with unequal alternating monocular exposure.

Thirty-four kittens reared by allowing each eye patterned visual input, but on alternate days and for unequal periods of time (unequal alternating monocular exposure (AME)), were tested for their ability to orient to targets at different positions in visual space. In all unequal AME cats, the visual field of the more experienced eye (MEE) was normal, while that of the less experienced eye (LEE) was restricted. In contrast, in 14 cats reared with equal AME, the fields of both eyes were equal and of normal size. The field deficits observed in the unequal AME cats must therefore be due to the imbalance in stimulation and thus result from a competitive interaction between the afferents from the MEE and the LEE. The field deficits observed in the unequal AME cats differed from those observed in two monocularly deprived (MD) cats. Neither of the MD cats ever responded to targets presented in the region of normal binocular overlap when tested with the deprived eye (DE). The unequal AME cats all showed a nasal field loss in the LEE, but responded normally to targets throughout the temporal portion of the binocular visual field. When the imbalance in stimulation was large (8 to 1) or moderate (8 to 4), there was an abrupt drop in responsiveness (from 100% to zero) as the position of the target was changed from temporal to nasal. When the imbalance was slight (8 to 7), the drop in responsiveness was more gradual and occurred within the nasal field. Our results demonstrate that (1) the paradigm of unequal AME is a useful one for studying binocular competition quantitatively, (2) even the slightest imbalance in stimulation of the two eyes can affect the outcome of the competitive interaction, and (3) the pathways serving binocular vision are not uniformly affected by binocular competition: the ipsilateral pathway is more sensitive than the contralateral pathway.

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PubMed1980

Unequal alternating monocular deprivation causes asymmetric visual fields in cats.

Kittens were reared so that each eye received normal patterned vision on alternate days. If the eyes received equal periods of stimulation, the visual fields were normal. If one eye received much more experience than the other, the field of the less experienced eye was restricted to the temporal hemifield. This change, which differs from that observed when one or both eyes are deprived continuously of patterned input, suggests that an imbalance in the duration of stimulation can influence the outcome of the normal competitive interaction between pathways from the two eyes and can cause a selective suppression of a portion of the input from the less experienced eye. This suppression may involve the ipsilateral retino-geniculo-cortical pathways or it may involve the entire cortical pathway from the less experienced eye, leaving the colliculus to control responses to visual targets.

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PubMedDate not supplied

Microglia in the nerve fiber layer of the cat retina: detection of postnatal changes by a new monoclonal antibody.

This paper describes changes in the appearance and distribution of microglia in postnatal cat retina as demonstrated by a new antibody, H386F. This fractionated IgM antibody was created via an intrasplenic immunization of a single BALB/C mouse with about 2-3 x 10(5) large, whole cells isolated from 46 minced cat retinae. To confirm that the labeled cells are microglia, the staining properties of H386F were compared with those of four commercially available antibodies, OX-33, OX-41, OX-42, and ED-1, that have been used by others to distinguish between microglia and other cells in rat brain. These experiments show that H386F is the only antibody of the five to label only microglia in both the cat retina and hippocampus.

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PubMedDate not supplied

Alternating monocular exposure increases the spacing of ocularity domains in area 17 of cats.

Goodhill (1993) has recently suggested that the spacing of ocularity domains in visual cortex is not solely an intrinsic property of cortex, but is determined, at least in part, by the degree of correlation in the activity of the two eyes. In support of this model, Löwel (1994) has shown that strabismus, which decorrelates the activity of the two eyes, increases the spacing of ocular dominance columns in area 17, but not area 18, of the cat. As a further test of Goodhill's model, in this paper we examine the effects of another rearing procedure that decorrelates the activity of the two eyes, namely alternating monocular exposure (AME). Cats were reared either normally (9 cats) or with AME (21 cats). We labeled their ocularity domains by one of three methods: ocular dominance columns by 2-deoxyglucose (14 cats), and ocular dominance patches by transneuronal transport (14 cats), or by injections of tracer into single layers of the lateral geniculate nucleus (LGN; 2 cats). The spacing of ocular dominance was 11% greater in the AME cats than in the normal cats (0.976 vs. 0.877 mm). These results are similar to those previously reported for strabismic cats, although the effect is less striking. We thus confirm that decorrelating the activity of the two eyes increases the spacing of cortical ocularity domains. Our results further suggest that the degree of decorrelation affects the extent of that increase.

Animals↗

PubMedDate not supplied

The monoclonal antibody H386F labels microglia in the retinal nerve fiber layer of several mammals.

The antibody H386F revealed microglia in the retinae of several species: owl monkey, slow loris, galago, ferret, raccoon, and tree shrew. The shape, size, and density of labeled microglia were identical to those labeled by OX-42 and OX-41, two antibodies specific for microglia, in both galago and owl monkey. The labeled microglia varied little in retinal location. There was remarkably little variability in density, shape, number, and size of the labeled microglia between species. All labeled microglia were evenly distributed across, but restricted to, the nerve fiber layer. Possible reasons for this restriction in location are discussed.

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