Portal-caudal vena caval-renal-hepatic arteriovenous malformation in a dog.
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Animals↗
Biomedical subjects
W C Hall
Publications and source records attributed to W C Hall.
Preliminary report: isolation of Ebola virus from monkeys imported to USA.
An epizootic caused by an Ebola-related filovirus and by simian haemorrhagic fever virus began among cynomolgus monkeys in a US quarantine facility after introduction of monkeys from the Philippines. This incident, the first in which a filovirus has been isolated from non-human primates without deliberate infection, raises the possibility that cynomolgus monkeys could be a reservoir of Ebola virus infection.
Animals↗
Cocaine abuse and its treatment.
Widespread use and abuse of cocaine have increased the frequency with which health professionals must manage acute and chronic intoxication and the complications stemming from drug ingestion. Acute intoxication from catecholamine excess progresses through three stages, affecting the cardiovascular, respiratory, and central nervous systems. Management is to support or return these systems to normal with sedation, beta blockade, and antiarrhythmics. Casual cocaine use is no longer considered benign, and numerous related medical complications are now recognized. Dopaminergic systems are the principal sites of reward and participate in abstinence symptomatology, putatively through depletion of dopamine and changes in receptor sensitivity and responsiveness. Long-term treatment approaches have focused on psychologic strategies of behavior modification and supportive psychotherapy. Pharmacotherapy with desipramine, amantadine, and bromocriptine was shown in preliminary studies to minimize the symptoms of cocaine withdrawal when used adjunctively with psychotherapy. The response to treatment may depend on the patient's premorbid psychiatric status.
Animals↗
Cholinergic innervation of the superior colliculus in the cat.
The superficial and intermediate gray layers of the superior colliculus are heavily innervated by fibers that utilize the neurotransmitter acetylcholine. The distribution, ultrastructure, and sources of the cholinergic innervation of these layers have been examined in the cat by using a combination of immuno-cytochemical and axonal transport methods. Putative cholinergic fibers and cells were localized by means of a monoclonal antibody to choline acetyltransferase (ChAT). ChAT immunoreactive fibers are distributed throughout the depth of the superior colliculus, with particularly dense zones of innervation in the upper part of the superficial grey layer and in the intermediate grey layer. Within the superficial grey layer, the fibers form a continuous, dense band, whereas within the intermediate grey layer the fibers are arranged in clusters or patches. Although the patches are present throughout the rostrocaudal extent of the superior colliculus, they are most prominent in middle to caudal sections. The structure of the ChAT immunoreactive terminals was examined electron microscopically. The appearance of the terminals is similar in the superficial and intermediate grey layers. They contain closely packed, mostly round vesicles, and form contacts with medium-sized dendrites that exhibit small, but prominent postsynaptic densities; a few of the terminals contact vesicle-containing profiles. To identify the sources of the cholinergic input to the superior colliculus, injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) were made in the superior colliculus and the sections were processed to demonstrate both the retrograde transport of WGA-HRP and ChAT immunoreactivity. Neurons containing both labels were found in the parabigeminal nucleus, and in the lateral dorsal and pedunculopontine tegmental nuclei of the pontomesencephalic reticular formation. Almost every cell in these nuclei that contained retrograde label was also immunoreactive for ChAT. The similarities between the laminar distributions of the ChAT terminals and the terminations of the pathway from the parabigeminal nucleus (Graybiel: Brain Res. 145:365-374, '78) support the view that the latter nucleus is a source of the cholinergic fibers in the superficial grey layer. The possibility that the pedunculopontine tegmental nucleus is a source of cholinergic fibers in the deep layers was tested by examining the distribution of labeled fibers following injections of WGA-HRP into this region of the tegmentum. Patches of labeled terminals were found in the intermediate grey layer that resemble in distribution the patches of ChAT immunoreactive fibers in this layer.(ABSTRACT TRUNCATED AT 400 WORDS)
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Collateral projections of predorsal bundle cells of the superior colliculus in the rat.
The deep layers of the superior colliculus contain cells which are premotor in the sense that they respond prior to the onset of shifts in gaze and send axons, by way of a pathway called the predorsal bundle, to the contralateral brainstem gaze centers and cervical spinal cord. Previous studies have suggested that these cells also contribute to other efferent pathways which arise in the deep layers. The present study examines the contributions of the cells of origin of the predorsal bundle to these additional pathways as a step toward understanding their roles in gaze mechanisms. In one series of experiments, retrograde tracers were used to compare the laminar distribution of predorsal bundle cells with the distributions of the cells of origin of three other pathways: those that project to the intralaminar region of the dorsal thalamus, those that project to the contralateral superior colliculus, and those that project to the ipsilateral brainstem tegmentum. Predorsal bundle cells were found primarily in stratum griseum intermedium sublayer b. This distribution overlaps extensively with the distribution of colliculus cells that project to the intralaminar region of the thalamus. In contrast, the majority of the colliculus cells that project to either the contralateral superior colliculus or the ipsilateral brainstem tegmentum do not overlap extensively with the predorsal bundle cells; instead, they are primarily located dorsal or ventral to sublayer b of stratum griseum intermedium. In a second series of experiments, two regions were injected with different retrograde fluorescent traces in single animals in order to study the collateral projections of the cells of origin of these pathways. The results indicate that many predorsal bundle cells project to the intralaminar region of the dorsal thalamus but that only a few contribute to the tectotectal pathway. The results also indicate that few tectotectal cells contribute to the ipsilateral tectobulbar pathway.
Animals↗
Comparison of Track XI fluorometric immunoassay with Bio-EnzaBead enzyme-linked immunosorbent assay for detection of serum antibody to mouse hepatitis virus.
The Track XI system (Microbiological Associates, Bethesda, Md.) was compared with the Bio-EnzaBead assay (Organon Teknika, Durham, N.C.) for the detection of antibody to mouse hepatitis virus (MHV). Strain A/J mice were inoculated intranasally with MHV type 3. Sera were collected at 1, 2, 4, and 9 weeks postinoculation and tested. Individual serum samples were retested twice by each method. The results suggested that the Track XI system was more sensitive and reliable than the Bio-EnzaBead assay in detecting antibody to MHV type 3 in individual serum samples from A/J mice.
Animals↗
Subcortical connections of the superior colliculus in the mustache bat, Pteronotus parnellii.
The mustache bat, Pteronotus parnellii, depends on echolocation to navigate and capture prey. This adaptation is reflected in the large size and elaboration of brainstem auditory structures and in the minimal development of visual structures. The superior colliculus, usually associated with orienting the eyes, is nevertheless large and well developed in Pteronotus. This observation raises the question of whether the superior colliculus in the echolocating bat has evolved to play a major role in auditory rather than visual orientation. The connections of the superior colliculus in Pteronotus were studied with the aid of anterograde and retrograde transport of wheat germ agglutinin conjugated to HRP. These results indicate that the superior colliculus of Pteronotus is composed almost entirely of the layers beneath stratum opticum. The retinal projection is restricted to a very thin zone just beneath the pial surface. Prominent afferent pathways originate in motor structures, particularly the substantia nigra and the deep nuclei of the cerebellum. Sensory input from the auditory system originates in three brainstem nuclei: the inferior colliculus, the anterolateral periolivary nucleus, and the dorsal nuclei of the lateral lemniscus. The projections from these auditory structures terminate mainly in the central tier of the deep layer. The most prominent efferent pathways are those to medial motor structures of the contralateral brainstem via the predorsal bundle and to the ipsilateral midbrain and pontine tegmentum via the lateral efferent bundle. Ascending projections to the diencephalon are mainly to the medial dorsal nucleus and zona incerta. Thus, the superior colliculus in Pteronotus possesses well-developed anatomical connections that could mediate reflexes for orienting its ears, head, or body toward objects detected by echolocation.
Afferent Pathways↗
A 13-week vapor inhalation study of 3,3-dimethyl-2-butanol in Sprague-Dawley rats.
Four groups of male and female Sprague-Dawley rats were exposed for 13 weeks to 3,3-dimethyl-2-butanol (PA) at concentrations of 0.00, 0.20, 1.00 or 5.00 mg/l (1 mg/l = 240 ppm). Exposures were for 6 hr per day, 5 days per week with sacrifices at 7 and 13 weeks of exposure, and at 4 weeks after exposure. The test animals were evaluated for abnormalities in physiology, behaviour, clinical laboratory parameters, and gross and microscopic morphology. No abnormalities were detected in electrocardiograms, respiratory indices, spontaneous activity, passive avoidance activity and open-field behaviour. Clinical signs related to PA exposure included alopecia, ataxia and lacrimation. There were no biologically significant between-group differences in body-weights during the study. The clinical laboratory data demonstrated a 30% increase in serum cholesterol and bilirubin at 7 weeks in high-dose males and an increase in urea nitrogen in intermediate and high-dose males at 13 weeks. There were no abnormalities in hematologic or coagulation parameters. At necropsy there were no significant gross abnormalities; however, examination of organ weights revealed enlarged kidneys in high-dose male rats at 13 weeks, enlarged ovaries in high-dose female rats at 13 weeks, and microscopic study of tissue sections revealed minimal to mild renal tubular injury in high and possibly intermediate dose males at several sacrifices. These findings suggest that the primary target organ of PA, when given by inhalation, is the kidney in male rats and possibly the ovary in female rats. The renal changes in the high-dose males were not fully reversible during the recovery period.(ABSTRACT TRUNCATED AT 250 WORDS)
Air Pollutants, Occupational↗
Thirteen-week oral toxicity study of methyl carbamate in rats and mice.
The purpose of this study was to identify the toxicologic effects produced by methyl carbamate in F344 rats and B6C3F1 mice. Administration of methyl carbamate by gavage five times a week for 13 weeks to male (50, 100, 200, 400, or 800 mg/kg) and female (62.5, 125, 250, 500, or 1000 mg/kg) rats resulted in dose-related lesions in the liver characterized by proliferative changes in hepatocytes consisting of foci of cellular alteration and frequent mitoses with atypical forms. Toxic alterations consisted of focal hepatocellular necrosis, pigmentation of Kupffer's cells, and the presence of basophilic inclusions resembling nucleoli in the cytoplasm of hepatocytes. Other toxic effects observed in rats were weight loss, testicular hypoplasia, bone marrow hyperplasia, and excessive pigmentation of the spleen. The survival of male and female rats was reduced following administration of the highest dose of methyl carbamate. In contrast to these findings, administration of the chemical to male (93.75, 187.5, 375, 750, or 1500 mg/kg) and female (125, 250, 500, 1000, or 2000 mg/kg) mice five times a week for 13 weeks resulted only in weight loss and inflammatory changes of the liver. The proliferative nature of the hepatic lesions observed in rats suggests that the compound is potentially hepatocarcinogenic.
Administration, Oral↗
The nigrotectal projection in the cat: an electron microscope autoradiographic study.
Recent evidence indicates that the nigrotectal tract plays an important role in regulating the premotor responses of cells in the in the intermediate gray layer of the superior colliculus. The purpose of the present study was to characterize the ultrastructure of nigrotectal terminals and of their postsynaptic targets in the intermediate gray layer. Nigrotectal terminals were identified in the electron microscope by labeling them autoradiographically, following injections of tritiated proline into the substantia nigra pars reticulata. The majority of nigrotectal terminals contain a high proportion of pleomorphic vesicles and form symmetrical synaptic contacts. Most of these terminals synapse with small dendritic profiles (2.00 micron +/- 0.83 SD), which may be the distal dendrites of neurons in the intermediate gray layer. Less than 10% of the labeled contacts are made with cell bodies or initial axonal segments.
Animals↗
Lack of mezlocillin and piperacillin interference in measurement of vancomycin in the Abbott TDx.
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Drug Interactions↗
The cerebellotectal pathway in the grey squirrel.
In the well laminated superior colliculus of the grey squirrel the cells of origin of the crossed descending pathway to the brainstem gaze centers are contained within the inner sublamina of the intermediate grey layer. The technique of anterograde transport of horseradish peroxidase was used to determine whether the pathway from the cerebellum to the superior colliculus terminates in this region. The technique of retrograde transport of horseradish peroxidase was used to localize the source of this pathway within the cerebellum and to determine the morphology of the cerebellotectal neurons. The grey squirrel cerebellotectal pathway provides two terminal fields to the superior colliculus: a diffuse projection into the deep grey layer and a more concentrated, interrupted projection into the inner sublamina of the intermediate grey layer. The more concentrated projection overlies precisely the tectal sublamina that contains the cells of origin of the predorsal bundle. In contrast to animals with frontal eyes, the cerebellotectal pathway in the grey squirrel was found to project almost entirely contralaterally and the vast majority of the cells of origin for the pathway were distributed ventrally, in the caudal pole of the posterior interpositus nucleus and the adjacent region of the dentate. The labelled cells in both cerebellar nuclei were large and displayed similar morphologies.
Animals↗
Evaluation of nonpalpable breast lesions. Experience in a training institution.
Biopsy directed by needle localization is a safe and relatively simple method of obtaining abnormal tissue for histologic examination without sacrificing surrounding normal breast tissue. In the setting of a training institution, accurate results can be expected as technical skills are obtained by a variety of housestaff. In this series of 70 biopsies, the lesion targeted on mammography was removed on the initial attempt in all but 1 instance, for an overall accuracy of 99 percent.
Adenofibroma↗
The sources of the nigrotectal pathway.
The nigrotectal pathway plays a role in the generation of saccade related responses by cells in the deep layers of the superior colliculus. By using a retrograde horseradish peroxidase technique that homogeneously fills neurons, the present experiments demonstrate that the source of the nigrotectal projection to the intermediate gray layer of the grey squirrel (Sciurus carolinensis) is a heterogeneous population of neurons whose somas and dendrites are concentrated in the rostral pole of pars reticulata. This region of pars reticulata receives projections from the posterior caudate, which in turn is a target of both the pulvinar and visual cortex. In addition, these experiments reveal the presence of a second, distinct set of neurons projecting to the midbrain tectum that are located in pars lateralis of the substantia nigra. These neurons can be distinguished from those in pars reticulata by their homogeneity and by their prominent basal dendrites. Furthermore, pars lateralis of the squirrel substantia nigra is, on cytoarchitectonic and immunocytochemical grounds, a distinct subdivision that does not receive projections from the posterior caudate. We conclude that both pars reticulata and lateralis are sources of the nigrotectal pathway. In addition, our results suggest, on connectional grounds, that the rostral pole of pars reticulata may be specialized to subserve the visual guidance of orienting movements.
Afferent Pathways↗
The transneuronal transport of horseradish peroxidase in the visual system of the frog, Rana pipiens.
During the course of experiments designed to study synaptic relationships between the terminals of retinal axons and the various cell populations in the optic tectum of the frog, Rana pipiens, we found that neurons in many of the retinorecipient nuclei, including the tectum, are labeled transneuronally following injections of horseradish peroxidase into the optic nerve. In the optic tectum, particular cell groups are labeled to the extent that their dendrites as well as their somas are filled with reaction product while other cell types, which, on the basis of the location of their somas or dendrites, seem equally likely to receive direct retinal projections, remain free of label. Electron microscopic investigation of the optic tectum reveals that the label is confined to pre- and postsynaptic processes. These results suggest that the transneuronal transport depends on a transfer of horseradish peroxidase from presynaptic terminals to postsynaptic cells rather than on a widespread diffusion of the enzyme through the neuropil followed by a selective uptake by particular cell groups. These results also suggest that only some of the tectal cell groups which receive direct retinal projections may be transneuronally labeled. The transneuronal transport of horseradish peroxidase is useful since it reveals the morphology as well as the location of at least some of the retinorecipient cells. Moreover, the robust nature of this phenomenon makes the frog a good choice for future studies of the mechanism of transneuronal transport.
Animals↗
Glutamate decarboxylase immunoreactivity in the intermediate grey layer of the superior colliculus in the cat.
Recent evidence suggests that gamma-aminobutyrate has a profound influence on the activity of premotor neurons in the intermediate grey layer of the superior colliculus. In the present study an antibody to glutamate decarboxylase, the synthesizing enzyme for gamma-aminobutyrate, was used to identify and characterize the structures in the intermediate grey layer of the cat that use gamma-aminobutyrate as a transmitter. The material was examined with both the light and electron microscope. Glutamate decarboxylase immunoreactivity was confined, for the most part, to axon terminals. Glutamate decarboxylase positive terminals almost completely cover the soma and proximal dendrites of the large neurons that are characteristic of this layer. Other glutamate decarboxylase positive terminals contact smaller, presumably more distal dendrites. By combining the glutamate decarboxylase immunocytochemistry with the retrograde transport of horseradish peroxidase in single animals, it was demonstrated that the cells of origin of the major descending efferent pathway from the intermediate grey layer, the predorsal bundle, are heavily contacted by glutamate decarboxylase immunoreactive terminals.
Animals↗
Nonintralaminar thalamostriatal projections in the gray squirrel (Sciurus carolinensis) and tree shrew (Tupaia glis).
In mammals, the corpus striatum receives prominent projections from the neocortex and from the intralaminar nuclei of the dorsal thalamus. The present study provides evidence based on anterograde degeneration and axonal transport that the corpus striatum also receives input from two nonintralaminar thalamic nuclei, the pulvinar and the medial geniculate body. Each of these nuclei projects to a separate region of the corpus striatum. Moreover, the same regions of the corpus striatum that receive projections from the pulvinar and medial geniculate body also receive projections from the cortical targets of these nuclei.
Animals↗
Relationships between the nigrotectal pathway and the cells of origin of the predorsal bundle.
The goal of this study was to define the anatomical relationships between the terminal field of the nigrotectal pathway and the tectal neurons which project to contralateral brainstem gaze centers by way of the predorsal bundle. The distribution and morphology of the cells of origin for the predorsal bundle were determined by using a modification of the retrograde horseradish peroxidase technique which homogeneously filled their somas and dendrites. The terminal distribution of the nigrotectal tract was determined using both anterograde horseradish peroxidase and autoradiographic procedures. The results indicate that, in the grey squirrel (Sciurus carolinensis), the predorsal bundle cells are a heterogeneous population whose dendritic fields form a well-defined band confined to the inner half of stratum griseum intermediate. This inner sublamina also can be identified in Nissl and myelin stains. The same sublamina is the major target of the nigrotectal tract. The striking anatomical correspondence between the distribution of nigrotectal terminals and the cells projecting in the predorsal bundle supports a proposal, based on recent physiological investigations, that the nigrotectal tract plays an important role in the initiation of the saccade-related activity of the deep tectal cells (Chevalier et al., '81; Hikosaka and Wurtz, '83a-d).
Animals↗