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Biomedical subjects

W C Hall

Publications and source records attributed to W C Hall.

At least 55 records · Page 3Linked to original sources
PubMed1984

Chronic toxicity and carcinogenicity evaluation of fenvalerate in rats.

Groups of 93 male and 93 female Sprague-Dawley rats were fed diets containing 1, 5, 25, and 250 ppm fenvalerate for up to 2 yr. The control group consisted of 183 males and 183 females. Approximately 10 treatment and 20 control rats/sex . group were killed at intervals of 3, 6, 12, and 18 mo. When body weights, food consumption, hematology, clinical chemistry and organ weights did not reveal a treatment effect, two additional groups of 50 males and 50 female rats were placed on 0 or 1000 ppm fenvalerate diets and maintained for 2 yr. Body weight was decreased and organ/body weight ratios were increased in brain, liver, spleen, kidneys (females), heart (females), and testes (males) in the 1000 ppm group. Mammary and pituitary tumors were commonly observed, along with a variety of other tumors occurring randomly among all control and treatment groups. No statistically significant differences in the number and type of neoplasms were observed except for mammary tumors in females in the main study. These effects were judged not to be toxicologically significant, since mammary tumor incidences did not exceed expected incidences in aged female Sprague-Dawley rats, time to tumor appearance was unchanged, and no shift in percent benign versus malignant tumors occurred. Sarcomas identified in the subcutis and dermis in 5/51 1000-ppm-treated males were also identified in 2% (1/50), 2% (2/102), and 0-6% of concurrent, original, and historical controls, respectively. Microscopic examination did not reveal any treatment-related lesions. The no-observable-effect level was determined to be 250 ppm.

Administration, Oral↗
PubMed1984

A comparison of the avidin-biotin-peroxidase complex (ABC) and peroxidase-anti-peroxidase (PAP) immunocytochemical techniques for demonstrating Sendai virus infection in fixed tissue specimens.

Mice were infected with Sendai virus and killed 8 days later. Lungs were removed and perfused with ethanol, 10% neutral formalin, Bouin's, B-5, or Zenker's fixatives. Tissues were dehydrated, embedded in paraffin, sectioned and stained for the presence of Sendai virus using the avidin-biotin-peroxidase-complex (ABC) and peroxidase antiperoxidase (PAP) immunocytochemical techniques. Results of these techniques were compared. The ABC technique was more sensitive than the PAP. Sendai antigen was demonstrated by the ABC technique in lung tissue fixed with any fixative, whereas antigen could be demonstrated with consistency only in ethanol-fixed lung by the PAP technique. Trypsin treatment of lung prior to immunoperoxidase treatment failed to enhance staining with either technique and actually caused a decrease in staining in ethanol, B-5 and Zenker's-fixed specimens.

Animals↗
PubMed1981

The normal organization of the lateral posterior nucleus in the golden hamster and its reorganization after neonatal superior colliculus lesions.

We have studied the normal organization of the hamster lateral posterior nucleus and its reorganization after neonatal superior colliculus lesions. First, we divided the lateral posterior nucleus into rostrolateral, rostromedial and caudal subdivisions and determined the normal distributions of terminals contributed to each division by the ipsilateral and contralateral superior colliculi, the ipsilateral posterior neocortex and the contralateral retina. Since the rostrolateral subdivision receives most of the projections from the ipsilateral superior colliculus, our studies concentrated on this region. The rostrolateral subdivision contains synaptic clusters formed primarily by medium-sized M-terminals synapsing around a central dendrite. Electron microscopic observations showed that the majority of M-terminals are from the ipsilateral colliculus, although a few are contributed by the contralateral colliculus and retina. Therefore, after an ipsilateral neonatal colliculus lesion the synaptic clusters must develop in the absence of their major input. The next step was to examine the distributions of the remaining afferents to the rostrolateral subdivision in adult animals which had received ipsilateral neonatal colliculus lesions. In the cases, the normally restricted projection fields of the contralateral colliculus and the retina expand until they share a border in the rostrolateral subdivision. In contrast the cortical projection, which normally extends throughout the lateral posterior nucleus, is reduced in the region containing retinal terminals. At the ultrastructural level, we found morphologically normal synaptic clusters and showed the M-terminals now occupying the clusters are contributed by the remaining colliculus and the retina. The results suggested that the afferents to the lateral posterior nucleus normally compete for synaptic space and that this competition continues after a neonatal colliculus lesion. In our final experiments, we performed various combinations of neonatal lesions (bilateral superior colliculus, superior colliculus and retina, superior colliculus and cortex) and found that the remaining afferent expand their terminal fields still further in the absence of two inputs.

Animals↗
PubMed1981

Aerosol Q fever infection of the nude mouse.

Athymic nude mice and euthymic littermate controls were exposed to 10(4) Coxiella burnetii organisms by small-particle aerosol. Antibody response with and without 2-mercaptoethanol treatment of serum was determined at various intervals after infection and serial kills were done to determine morphologic changes in both mouse phenotypes. Total antibody titers determined by the indirect fluorescent antibody technique to phase I and phase II C. burnetii were identical for both groups of mice. Microagglutinin titers determined on days 28 and 33 were abolished by 2-mercaptoethanol treatment of serum from both phenotypes, indicating that the antibody probably resided in the IgM fraction. Microscopically, the reaction to C. burnetii infection was similar in nude and euthymic mice on days 7 and 14. Later, the number and size of lesions attributable to Q fever diminished in euthymic mice. Infection was progressive in nude mice, with macrophage infiltration of most tissues, especially spleen and liver. Numerous rickettsiae were seen by immunofluorescence and electron microscopy in phagocytic vesicles of macrophages, many of which were dilated, giving the macrophage a vacuolated appearance. Results suggest that clearance of C. burnetii infection in mice is independent upon thymus-derived lymphocytes.

Aerosols↗
PubMed1981

The laminar origin and distribution of the crossed tectoreticular pathways.

The superior colliculus is the source of a prominent descending pathway which crosses the midline in the mesencephalon and projects to the paramedian pontine reticular formation. The primary goal of the present study was to identify the cells in the superior colliculus of the grey squirrel which give rise to this pathway by using a combination of anterograde and retrograde tracing techniques. Results from the anterograde studies demonstrated the course and terminal distribution of this pathway and suggested that its laminar origin is the intermediate grey layer, stratum griseum intermediale. The retrograde studies were used to confirm the results of the anterograde experiments and to provide a more quantitative estimate of the laminar distribution of the cells which give rise to this pathway. In most cases, over 90% of the cells retrogradely labeled following injections of horseradish peroxidase along the course of this pathway were located in the intermediate grey lamina. This origin is in contrast to that of the ipsilateral tectoreticular pathway which originates primarily in stratum griseum profundum (Holcombe, V., and W. C. Hall (1981) Neuroscience 6: 255-260) and suggests that these two grey layers of the deep tectum are functionally distinct.

Afferent Pathways↗
PubMed1980

The normal organization of the lateral posterior nucleus of the golden hamster.

As a first step in analyzing the influence of various afferent projections on the development of the hamster lateral posterior nucleus, its normal organization was studied using both light and electron microscopic techniques. Rostrolateral, rostromedial, and caudal subdivisions were identified. The rostrolateral subdivision receives dense projections from the ipsilateral superior colliculus and posterior neocortex, as well as sparser, more restricted projections from the contralateral colliculus and retina. The ipsilateral colliculus is by far the major source of medium-sized (M)terminals with round vesicles. These terminals synapse around the shafts of large central dendrites to form distinctive synaptic clusters. The contralateral colliculus and retina contribute a few M-terminals to the clusters. In contrast, axons from the posterior neocortex form very large (RL-)terminals with round vesicles from the posterior neocortex form very large (RL)terminals with round vesicles which synapse onto numerous appendages of single proximal dendrite, are surrounded by glial lamellae, and rarely participate in the clusters. Axons from all four sources also form small (RS)terminals with round vesicles which synapse on the shafts of small dendrites. Finally, F-terminals with flat or pleomorphic vesicles form symmetric synaptic contacts both within and outside the clusters. The only identified projection to the rostromedial subdivision is from the ipsilateral posterior neocortex, which contributes RL- and RS-terminals. F-terminals are also found, but neither M-terminals nor synaptic clusters are present. The caudal subdivision also receives RL- and RS-terminals from the ipsilateral posterior neocortex. Small inputs from the ipsilateral and contralateral colliculi are present, but their axons form only RS-terminals. No M-terminals or synaptic clusters are found. These results indicate that a large neonatal superior colliculus lesion would eliminate the vast majority of the M-terminals in the synaptic clusters of the ipsilateral lateral posterior nucleus. In subsequent studies (Crain and Hall, '80 a,b,c), we will examine how the remaining inputs from the retina, contralateral superior colliculus, and posterior neocortex contribute to the synaptic organization when it develops after such a lesion.

Animals↗
PubMed1980

The organization of the lateral posterior nucleus of the golden hamster after neonatal superior colliculus lesions.

The reorganization of the adult hamster's lateral posterior nucleus after neonatal superior colliculus lesions was studied using primarily light and electron microscopic degeneration techniques. Two types of experiments were conducted. First, the distributions of the remaining afferents from the contralateral superior colliculus, the cotralateral retina, and the ipsilateral posterior neocortex were determined using the Fink-Heimer ('67) technique. Normally the projections from the contralateral superior colliculus and retina are sparse and restricted to small areas in the rostrolateral subdivision. After neonatal lesions of the ipsilateral colliculus, however, these two minor projections greatly increase in density and expand to share a common border. In contrast, the normal projection from the posterior neocortex is dense throughout the rostrolateral subdivision. After a neonatal colliculus lesion, however, this projection is greatly decreased in the region occupied by the optic tract terminals. Second, the ultrastructural organizatin of the rostrolateral subdivision was studied in adult animals whhich had received neonatal colliculus lesions. Normally, this region is characterized by synaptic clusters in which numerous medium-sized terminals (M-terminals), almost all from the ipsilateral colliculus, synapse around the shaft of a large central dendrite. The contralateral colliculus and retina normally contribute only a few M-terminals. After a neonatal colliculus lesion, typical clusters still form, but now the expanded projections from the contralateral colliculus and retina contribute numerous M-terminals. The cortex does not contribute M-terminals in either normal or experimental animals. These results suggest that the afferents to the rostrolateral subdivision normally compete for synaptic space. The various factors that might be involved in determining the outcome of such competition are discussed.

Animals↗
PubMed1980

The organization of afferents to the lateral posterior nucleus in the golden hamster after different combinations of neonatal lesions.

After a neonatal lesion of the ipsilateral superior colliculus, the projections to the lateral posterior nucleus from the contralateral superior colliculus and retina expand their terminal fields until they share a common border. In the first experiment described in this paper, we removed both superior colliculi at birth and used the Fink-Heimer method to show that the optic tract projection could expand even further and enter the region which would have been occupied by the terminals of the crossed colliculus projection. Similarly, in the second experiment, we showed that the crossed collicular projection could be increased even more if the contralateral eye as well as the ipsilateral colliculus was removed at birth. Another result of a neonatal superior colliculus lesion is that the projection from the optic tract shares a border with the posterior neocortical projection. In the third experiment, we removed both the ipsilateral superior colliculus and the posterior neocortex at birth and demonstrated that the optic tract projection expanded more than after an ipsilateral colliculus lesion alone. Our results support the hypotheses that the projections from the ipsilateral and contralateral superior colliculi and the retina compete for synaptic space in the lateral posterior nucleus, and that a similar competition between the retinal and cortical projections may also occur.

Animals↗
PubMed1979

Laminar origin of projections from the superficial layers of the superior colliculus in the tree shrew, Tupaia glis.

The laminar origin of the efferent projections from the superior colliculus to the pulvinar and to the dorsal and ventral lateral geniculate nuclei has been studied using the retrograde axonal transport of horseradish peroxidase. Following injections in either the dorsal or the ventral lateral geniculate nucleus, cells heavily labeled with the horseradish peroxidase reaction product are restricted primarily to the upper stratum griseum superficiale. These cells have small, fusiform somas with dendrites which extend dorsally and ventrally, perpendicular to the pial surface. In contrast, following injections in the pulvinar, cells labeled with reaction product are restricted primarily to the lower stratum griseum superficiale and to the most superficial part of stratum opticum. These cells typically have larger somas than cells in the upper stratum griseum superficiale, and often have dendrites which emerge horizontally from the cell body. When taken together with previous electrophysiological and anatomical studies, the present findings suggest that there is a laminar subdivision of the tree shrew stratum griseum superficiale, and that these subdivisions project selectively to different thalamic targets.

Animals↗
PubMed1979

Melanotic neuroectodermal tumor of infancy. An ophthalmic appearance.

Fullness developed in the left side of a 5-month-old male infant's face in the region of the zygoma. An incisional biopsy specimen showed the mass to be a melanotic neuroectodermal tumor, and radical excision was performed. There has been no recurrence of the tumor one year later. Tumors of this type occur in the face, particularly in the maxilla, and have only rarely been reported around the orbit.

Humans↗
PubMed1979

Exposure of guinea pigs to Rickettsia rickettsii by aerosol, nasal, conjunctival, gastric, and subcutaneous routes and protection afforded by an experimental vaccine.

Guinea pigs were inoculated with Rocky Mountain spotted fever by the aerosol, conjunctival, subcutaneous, intragastric, and intranasal routes. Rickettsial infection was produced by all routes except intragastric. All animals with clinical signs of disease developed agglutinating antibody, and most developed a cell-mediated immune response. Disease produced by all experimental routes (except intragastric) was indistinguishable. The tissue culture-derived inactivated vaccine produced in this laboratory protected guinea pigs against an aerosol challenge.

Administration, Intranasal↗
PubMed1978

The medial geniculate body of the tree shrew, Tupaia glis. I. Cytoarchitecture and midbrain connections.

In this study of the medial geniculate body in the tree shrew eight subdivisions are identified on the basis of differences recognized in Nissl-stained material. Experiments using the methods of anterograde and retrograde axonal transport and anterograde degeneration show that each subdivision has a unique pattern of connections with the midbrain. The ventral division of the medial geniculate body contains at least two subdivisions, the ventral nucleus and the caudomarginal nucleus. The ventral nucleus is characterized by densely-packed cells and receives topographically organized projections from the central nucleus of the inferior colliculus. The caudomarginal nucleus, on the other hand, receives its major midbrain projections from the medial nucleus in the inferior colliculus. In the dorsal division four subdivisions are distinguished. The suprageniculate nucleus contains large, loosely-packed cells and receives projections from the deep layers of the superior colliculus and from the midbrain tegmentum. The dorsal nucleus receives projections from the midbrain tegmentum. The deep dorsal and anterodorsal nuclei have neurons which resemble those in the dorsal nucleus. Both receive projections from the roof nucleus of the inferior colliculus but the deep dorsal nucleus receives an additional projection from the parabrachial tegmentum. The medial division has a rostral and a caudal subdivision. The ascending projections to the rostral nucleus are from the lateral zone in the inferior colliculus and from the spinal cord. The caudal nucleus contains cells with large somas and receives projections from most of the midbrain areas which project to the other subdivisions of the medial geniculate body.

Animals↗
PubMed1978

The medial geniculate body of the tree shrew, Tupaia glis. II. Connections with the neocortex.

In this study the temporal cortex of the tree shrew was subdivided on the basis of cytoarchitectonic criteria, and the connections of each subdivision with the thalamus and midbrain were analyzed with retrograde and anterograde techniques. The results indicate that, with one exception, each subdivision of the medial geniculate body projects to a separate cortical area. The primary auditory cortex receives projections from the ventral nucleus. Surrounding the primary cortex are at least five additional cytoarchitectonically distinct areas which receive projections from the remaining medial geniculate subdivisions. The evidence suggests that there is very little overlap in the projections from each of these geniculate subdivisions. An exception is the projection of the caudal nucleus of the medial division. This subdivision apparently projects to most, if not all, of the cortical target of the medial geniculate body. Although the cortical projections of the caudal nucleus overlap those of the other medial geniculate subdivisions, the laminar distribution of its terminations in cortex is different. The caudal nucleus projects primarily to layer VI whereas the other subdivisions of the medial geniculate body project primarily to layer IV and the adjacent part of layer III. Anterograde techniques were also used to study the projections from the cortex back to the thalamus and to the midbrain. The projections to the thalamus precisely reciprocate the thalamocortical connections. The projections to the midbrain are to the same areas which the preceding study (Oliver and Hall, '78) showed give rise to ascending projections to the medial geniculate body. An exception is the central nucleus of the inferior colliculus which apparently does not receive a projection from the temporal cortex.

Animals↗
PubMed1978

The organization of central auditory pathways in a reptile, Iguana iguana.

The present experiments were designed to trace the central auditory pathways in an extant reptile, the New Worlkd lizard--Iguana iguana, utilizing anterograde axonal degeneration stained by the Fink-Heimer ('67) method and the retrograde axonal transport of horseradish peroxidase (LaVail and LaVail, '74). Beginning with the projections of the auditory portion of the VIIIth nerve, the ascending pathways were traced through successive relay nuclei to the telencephalon. The auditory portion of the VIIIth nerve projects to two nuclei in the dorsomedial medulla-nucleus angularis and nucleus magnocellularis medialis. These two nuclei together with a third cll group, nucleus magnocellularis lateralis (intercalated between nucleus angularis and nucleus magnocellularis medialis), have been referred to as the auditory tubercle in previous studies (cf. Miller, '75). The axonal degeneration following large lesions of the auditory tubercle and small lesions of nucleus angularis demonstrated the second order auditory pathways. Fibers leave nucleus angularis ventrally and travel to the ventral surface of the medulla where they cross the midline and ascend to the midbrain in pathways resembling the trapezoid body and the lateral lemniscus of mammals. Along these pathways, terminal arborizations of some fibers were seen in three lower brainstem nuclei while other fibers ascent to the midbrain and terminate in the central nucleus of the torus semicircularis. Experiments in which horseradish peroxidase injections were made in the torus semicircularis demonstrated that nucleus angularis is a primary source of second order auditory fibers to the midbrain and, in addition, that two of the lower brainstem targets of the auditory tubercle project to the torus semicircularis. These lower brainstem pathways were shown to be associated with the auditory system by electrophysiologically recording sound-evoked responses from clusters of cells in the torus semicircularis. Ascending fibers arising from the central nucleus of the torus semicircularis were followed rostrally where they entered the dorsal thalamus and terminated throughout nucleus medialis. Finally, a thalamotelencephalic auditory pathway was traced from nucleus medialis into the lateral forebrain bundle. Terminations of this pathway from nucleus medialis were seen in the medial dorsal ventricular ridge and in the striatum. It was concluded that the ascending auditory pathways of the iguana bear a remarkable resemblance to both the mammalian and avian auditory pathways from the level of the first order neurons in the VIIIth nerve to the level of the telencephalon. At the same time, there are important specializations of the auditory system in birds and mammals such as the development of particular lower brainstem nuclei. Nevertheless, a basic plan for the organization of the auditory system in terrestrial vertebrates can be recognized which invites comparisons with the vertebrate classes that remained in aquatic habitats...

Animals↗