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Biomedical subjects

J E Cook

Publications and source records attributed to J E Cook.

At least 55 records · Page 3Linked to original sources
PubMed1986

Impaired refinement of the regenerated retinotectal projection of the goldfish in stroboscopic light: a quantitative WGA-HRP study.

The retinotectal projection of the goldfish was studied after regeneration of a cut optic nerve in stroboscopic light, constant light or diurnal light, with the lens removed to blur the retinal image. Retrograde transport of wheatgerm agglutinin, conjugated to horseradish peroxidase, from a standard tectal injection site was used to measure the topographic precision of the projection. The dispersion of labelled retinal ganglion cells, which reflects this precision, was assessed by a method based on distance to nearest neighbour. In normal fish treated similarly, these cells are known to be clustered into about 1% of the retinal area. Early in regeneration, however, they are widely dispersed. The projection map then re-acquires its precision over two or three months. In diurnal light, lens ablation had no effect on refinement of the regenerated map. Constant light increased the number of labelled cells but also had no significant effect on the map. But in stroboscopic light with a continuous pseudorandom pattern of flash intervals (average rate 4.8 Hz), much less refinement was seen. Even after 70-98 days of regeneration, labelled cells remained scattered, on average, over 20% of the retinal area. These retinae were indistinguishable by several criteria from those obtained in diurnal light after only 32-39 days. Mislocated axon terminals, which are largely eliminated during the second and third months of regeneration in diurnal light, evidently persist much longer in stroboscopic light that synchronizes ganglion cell activity across the retina. These results, like previous ones obtained by blocking the transmission of activity to the tectum, support a model of map refinement based on correlation in the firing of neighbouring neurons, which may have wide application within the nervous system.

Animals↗
PubMed1985

Tritan discriminations by 1- and 2-month-old human infants.

The capacity of 1- and 2-month-old infants to make a tritan discrimination between a 4 degree, 416 nm test field and a 547 nm surround was tested by means of the forced-choice preferential looking technique. Most of the 2-month-olds and the other 1-month-olds made the tritan discrimination and must therefore have functional SWS cones. Most of the youngest 1-month-olds failed to make the tritan discrimination and therefore either do not encode or do not preserve the information ordinarily encoded by SWS cones. The implications of these data and the prior data of Hamer et al. [Vision Res. 22, 575-587 (1982)] are discussed in relation to color theory.

Adult↗
PubMed1984

Use of a lectin-peroxidase conjugate (WGA-HRP) to assess the retinotopic precision of goldfish optic terminals.

The lectin wheat-germ agglutinin (WGA), conjugated to horseradish peroxidase (HRP), is an effective tracer for goldfish optic axons. Under suitable conditions, WGA-HRP injected iontophoretically into the normal goldfish tectum is taken up by retinotopic optic terminals (but not by axons of passage) and labels a small, discoid patch of retinal ganglion cells. Under identical conditions, unconjugated HRP is mainly taken up by injured axons of passage. WGA-HRP injected into the tectum after regeneration of the contralateral optic nerve again labels a small patch of ganglion cells, demonstrating the extent to which regenerated terminals are also retinotopic.

Animals↗
PubMed1984

Comparative aging changes in canine uterine tubes (oviducts): electron microscopy.

Uterine tubes (oviducts) from 20 dogs in 3 age groups were evaluated by scanning electron microscopy. Three segments of the left uterine tube from 4 prepubertal dogs, 8 middle-aged dogs (4 to 6 years), and 8 aged dogs (8 to 11 years) were collected after euthanasia or ovariohysterectomy. Specimens were collected while the dogs, except for one in the middle-aged group, were in late metestrus or anestrus (to reduce variation in tubal epithelium by estrogen stimulation). Subdivision of mucosal folds, invaginations of mucosa into the entire length of the folds, and height of the folds, increased with age; the width of the mucosal folds had decreased. Complete dedifferentiation of epithelium of the uterine tube ampulla and isthmus to nonciliated cells in a few aged dogs resembled changes in postmenopausal women. In 3 prepubertal dogs, cilia were present in the infundibulum of the uterine tube, but not in the ampulla and isthmus. In a late prepubertal dog, early ciliation of ampulla and isthmus began before first estrus. Nonciliated cells with a single central cellular projection were present in all segments and all age groups. The significance of the projection was discussed.

Aging↗
PubMed1983

A pattern of optic axons in the normal goldfish tectum consistent with the caudal migration of optic terminals during development.

Optic axons were cut in the goldfish optic nerve or tectum, filled with horseradish peroxidase and traced in tectal wholemounts. Many of them ran in conspicuous fascicles which curved across the tectum. Axons from central nasal retina, which ran in the most rostral fascicles, turned abruptly as they left these fascicles; ran caudally in a diffuse, parallel array for up to half the tectal length; and passed beneath more caudal fascicles to innervate the caudal half-tectum. Axons from peripheral nasal retina ran in the most caudal fascicles and terminated near their turning-points. Axons from temporal retina entered the tectum at its rostral margin and ran caudally from their points of entry to innervate the rostral half-tectum. The resultant pattern was entirely consistent with the proposal that a slow caudal migration of optic terminals compensates during normal development for disparate modes of retinal and tectal growth.

Animals↗
PubMed1983

Consequences of misrouting goldfish optic axons.

Cut optic axons regenerate into the goldfish tectum by indirect routes. To study the accuracy with which they terminate we made visuotectal maps before and immediately after cutting through the rostral tectum from its medial edge. This severed the normal pathway to medial tectum leaving intact only grossly misrouted axons. In fish mapped in this way, 3 months or more after contralateral optic nerve cuts, each initial map was essentially normal. After a tectal cut the electrical responses were usually weaker; but their receptive field positions proved to match very closely those noted previously for the same recording sites. The mean angular change was only 8.48 degrees and much of this could be accounted for by experimental errors. In fish mapped 6 months or more after attempts to cross-unite the optic tract brachia, initial maps were less regular. Some showed gross rearrangement of groups of terminals; and recognizable irregularities persisted in two fish mapped again after a further 4 or 5 months. However, maps made after tectal cuts in such fish were not noticeably less regular than the initial maps. Field position changes averaged 17.85 degrees. In both groups misrouted axons, filled with horseradish peroxidase after mapping and visualized in whole-mounts, crossed the tectum from lateral regions to reach the medial recording sites. The small field position changes in both groups confirm that axons from detectable terminals only among their retinal neighbours; nevertheless the irregular maps seen after tract cross-union lead us to expect the orderly arrangement of the normal pathway to contribute significantly to the precision of the normal map.

Animals↗
PubMed1982

Errant optic axons in the normal goldfish retina reach retinotopic tectal sites.

Optic axons in the goldfish retina generally run radially from their origins to the optic nerve. However, horseradish peroxidase (HRP), introduced into small groups of axons through lesions in the tecta of normal fish, consistently filled some which ran parallel to the retinal margin for long distances before turning centrally. Since all the HRP-filled ganglion cells lay close together, their axons evidently reached adjacent tectal sites by these widely divergent routes.

Afferent Pathways↗
PubMed1980

Diagnosing ovine epididymitis by immunofluorescence.

Antisera against Actinobacillus seminis, Brucella ovis and Corynebacterium pseudotuberculosis were prepared in adult female goats. Specific immunofluorescence was observed in cultural smears of A seminis, B ovis and C pseudotuberculosis by the direct technique and in smears of A seminis also by the indirect technique. Individual organisms could be recognised. Specific fluorescence of A seminis was readily detected in semen. The results indicate that immunofluorescence may offer an effective method for rapidly and accurately diagnosing bacterial epididymitis in sheep, especially before epididymal lesions are palpable.

Actinobacillus↗
PubMed1979

Serologic survey for leptospirosis in coyotes in northcentral Kansas.

During 1975 to 1977, serum samples were collected from 101 adult coyotes (Canis latrans) captured in northcentral Kansas. Ten samples were seropositive by microagglutination testing and six of those samples were seropositive for multiple serovars. Titers for Leptospira interrogans serovars grippotyphosa, pyrogenes, djasiman, butembo, and pomona were demonstrated.

Animals↗