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M L Cooper

Publications and source records attributed to M L Cooper.

At least 91 records · Page 5Linked to original sources
PubMed1981

Coexistence of neuronal and glial precursor cells in the cerebral ventricular zone of the fetal monkey: an ultrastructural immunoperoxidase analysis.

The cytological composition of the proliferative zones in the fetal monkey occipital lobe was examined at the light and electron microscopic levels by immunoperoxidase localization of glial fibrillary acid protein (GFA), a protein that is present in astrocytes and radial glial cells but not neurons. During the peak of neurogenesis at embryonic day 80, two distinct classes of proliferative cells, GFA-positive and GFA-negative, are intermixed in the ventricular and subventricular zones. Both cell types are readily recognized in different phases of the mitotic cycle along the ventricular surface. The results indicate that, contrary to prevailing views, (1) glial and neuronal cell lines coexist within the fetal proliferative zones and (2) the onset of glial phenotypic expression occurs prior to the last cell division.

Animals↗
PubMed1981

Effect of fusarium T-2 toxin on hematological and biochemical parameters in the rabbit.

The single intravenous administration of purified T-2 toxin to rabbits to 0.5 mg per kg body weight produced a decrease in hematocrit, while blood cell count, and serum alkaline phosphatase activity. The plasma clotting time, as measured by the activated partial thromboplastin time assay, was prolonged after intravenous T-2 toxin administration. In contrast, the administration of T-2 toxin to rabbits at 2.0 mg per kg body weight by gastric intubation produced oral lesions, diarrhea and anorexia in the animals but did not cause significant alteration in hematological and biochemical parameters. The results suggest that the rabbit may be a suitable model for further examination of the biochemical mechanisms involved in the cytotoxic action of T-2 toxin.

Administration, Oral↗
PubMed1980

Regional variation in the representation of the visual field in the visual cortex of the Siamese cat.

In Siamese cats, many ganglion cell fibers from the temporal retina misproject to the contralateral hemisphere; as a result, each lateral geniculate nucleus contains an abnormally large representation of the ipsilateral visual field. The manner in which the visual cortex processes this aberrant visual information has been examined in several previous studies. In some Siamese cats, the region of the 17/18 border was found to contain an extensive, systematic map of the ipsilateral field, while in other animals no such map was found, and the 17/18 border appeared to represent the zero meridian of azimuth (as in normal cats). These results have led to the suggestion that there are two distinct types of Siamese cat ("Boston" and "Midwestern") which can be distinguished on the basis of cortical topography and the anatomical organization oif the geniculocortical pathway. In the present study, we have recorded from four Siamese cats in order to examine the visual field map in the region of the 17/18 border; in each cat we recorded at anterior coronal levels corresponding to the representation of the lower visual field, and also at more posterior levels near the horizontal meridian representation. In all of the animals we found that the anterior penetrations (corresponding to mean receptive field elevations inferior to -7 degrees) yielded 15-20 degrees of ipsilateral field representation at the 17/18 border; however, the posterior, horizontal meridian penetrations (with mean elevations from +1 degrees to -4 degrees) showed excursions of only about 5 degrees into the ipsilateral field. This large difference in the representation of azimuth was not due to rotation of the eyes during our recording sessions. The finding of appreciable differences in the amount of ipsilateral field represented at different anterior-posterior levels of the same animal might lead to the suggestion that there are not two distinct populations (or types) of Siamese cat with regard to the cortical map of the ipsilateral field. Rather, we raise the possibility that Siamese cats form one population in which there is a continuous variation in the extent of ipsilateral field represented in the cortex.

Animals↗
PubMed1979

The decussation of the retinothalamic pathway in the cat, with a note on the major meridians of the cat's eye.

We have studied the naso-temporal division of the retinothalamic pathway of the cat by making large unilateral injections of horseradish peroxidase into the lateral geniculate nucleus. In confirmation of previous work, our retinal whole-mounts show a distinct vertical decussation line separating the contralaterally projecting nasal retina from the ipsilaterally projecting temporal retina. The ipsilateral decussation line is quite sharp, while the contralateral decussation is somewhat more diffuse, with numbers of large cells extending a few degrees into the temporal retina. However, in contrast to the results of optic tract section, our material (demonstrating the thalamic component only) does not reveal any significant population of contralaterally projecting small cells across most of the temporal retina. The previous observation of approximately 200 micrometer of naso-temporal overlap in the area centralis is confirmed here, and evidence is presented that this overlap may increase at eccentricities above the horizontal meridian. Taken together with previously published data, this demonstration of the vertical decussation line has allowed us to estimate the relative inclinations of the major meridians of the cat's eye.

Animals↗
PubMed1979

The retinothalamic pathways in Siamese cats.

By injecting one lateral geniculate nucleus with large amounts of horseradish peroxidase (HRP), we have determined the retinal distributions of contra- and ipsilaterally projecting retinothalamic ganglion cells in the Siamese cat. In accord with the data of others, we observe that large numbers of temporal ganglion cells, which normally send axons ipsilaterally, instead misproject to the contralateral thalamus. However, in contrast to the expectations raised by previous work, we do not find the Siamese defect to be a simple 20 degrees shift of the naso-temporal decussation line. Rather, there is intermingling of the crossed and uncrossed retinothalamic populations in the temporal retina, with a gradual increase in the proportion of ipsilaterally projecting ganglion cells as one moves temporally. Thus, the Siamese abnormality represents not only a temporal displacement of the retinothalamic decussation line, but also a smearing of the normally rather sharp division between regions of ipsilateral and contralateral projection. Cell size measurements and anterograde transport of H3-proline confirm the HRP findings and suggest differential effects of the Siamese abnormality according to ganglion cell class. In particular, it appears that the large ganglion cells to misproject to a greater degree than the rest of the retinothalamic population.

Animals↗
PubMed1979

A neurophysiological determination of the vertical horopter in the cat and owl.

We have undertaken a determination of the vertical horopter in two species by simultaneously mapping the receptive field positions of binocular cortical neurons at various elevations along the zero azimuthal meridians. In the paralyzed cat our recordings show that the zero meridians of the two eyes are parallel and vertical under paralysis. Slit-pupil photographs demonstrate that paralysis induces an average net intorsin of 9 degrees between the two eyes. Correction back to the unparalyzed state results in the zero meridians themselves being out-torted with respect to each other. Since the two eyes' zero meridians define physiologically the positions of corresponding retinal points, this out-torsion results in a vertical horopter in the mid-sagittal plane which is tilted away from the alert, unparalyzed cat. The limited eye movements of the owl permit the use of an unparalyzed preparation; it is therefore possible to avoid the problem of the cyclotorsion under paralysis which occurs in the cat. The results of our physiological analysis in the burrowing owl (Speotyto cunicularia) also reveal a tilted horopter in this terrestrial avian species.

Animals↗
PubMed1979

Improved use of tapetal reflection for eye-position monitoring.

A new technique is described for eye-position monitoring in species with strong tapetal reflections. A fiber optic is used to introduce light into the eye, whose optics then produce an image of the fundus on a tangent in front of the animal. The technique simplifies heretofore tedious measurement of cylotorsional changes, as well as providing a very wide view of the fundus. It has been used successfully in conjunction with single-unit recording from the visual system.

Animals↗
PubMed1970

The experimental modification of teacher attending behavior.

A method of observing and modifying teacher attention to appropriate child responses in preschool classrooms was developed. Two teachers with no formal training in reinforcement principles were observed for a baseline of eight days. Teacher A, who displayed a lower baseline rate of attending to appropriate child responses, was trained first. Teacher B was simply observed during the first part of the training condition for Teacher A. During training, A received feedback which included definitions of appropriate child responses, her frequency of attending to appropriate child responses, her total percentage of attending to appropriate child responses, and her frequency of failing to attend to appropriate child responses. Teacher B was then trained in a similar way. Both teachers showed an increase in attending to appropriate child responses subsequent to the onset of experimental feedback.

Journal Article↗
PubMed1966

Seasonal variation in mating behavior in cats after desensitization of glans penis.

The glans penis in 14 sexually experienced cats was desensitized by section of the nerves dorsalis penis. These males mounted the estrous female readily but they were so disoriented that they could not achieve intromission. Reduced sensory feedback resulting from the operation and from lack of intromissions caused a decided drop in sexual activity in the fall with recovery in early winter. A latent sexual cycle in male cats is revealed, which corresponds in time to the established female cycle.

Animals↗
PubMedDate not supplied

Social network drinking and adult alcohol involvement: a longitudinal exploration of the direction of influence.

Past research shows consistent associations between individuals' drinking patterns and the drinking patterns of their social network members. This association has usually been attributed to the influence of social networks on individual behavior. Recent studies concerning adolescent drinking behavior suggest that such associations may be due, in part, to selection effects in which individuals form social ties with those who have drinking habits similar to their own. The present study used longitudinal data and structural equation modeling to compare the selection and influence effects among a large representative sample of adults. Results suggested that both selection and influence affect the association between individual and network drinking patterns among adults, but that social selection effects are substantially stronger than social influence effects. A cross-lagged structural equation model with a normed fit index of .975, showed that the path indicating peer influence had a coefficient of .069 (P<.01), whereas the path indicating network selection had a coefficient of .193 (P<.01). Comparisons across age, race, sex, and marital status groups revealed similar results, with stronger selection than influence effects for all groups.

Adolescent↗