Search PubMed⌕ Search

Biomedical subjects

N L Strominger

Publications and source records attributed to N L Strominger.

At least 37 records · Page 2Linked to original sources
PubMed1985

Morphological changes in the cochlear nuclear complex in primate phylogeny and development.

The primate cochlear nuclear complex exhibits several characteristic morphological differences in the various primate families from Lorisidae through Hominidae. The most striking differences occur in the organization of the dorsal cochlear nucleus in which the laminar pattern becomes progressively obscured. Granule cells form an external granular layer as well as being intermixed within the molecular and pyramidal layers in slow lorises and squirrel and rhesus monkeys. Whereas a prominent external granular layer remains in chimpanzees, granule cells are scant in other portions of the nucleus. Human adults lack an external granular layer. A small number of granule cells occur but with inconstant distribution. Primates lack the linear array of pyramidal cells oriented perpendicularly to the epithelial surface as seen in cats. The granule cell layer exhibits similar regression in development of the human cochlear complex. The external granular layer is prominent in the fetus but rapidly decreases in size after birth. It achieves its adult form prior to 18 months. The data suggest that neuronal attrition, or programmed cell death, may be the major mechanism accounting for the alterations that occur in the human granule cell layer. Other differences in cytoarchitecture, within the great apes and humans, include decreases in the small and giant cell populations of the cochlear complex. These changes, in consort with the organizational changes and reduction of granule cells as noted above, suggest a trend towards reduced intranuclear integration at the level of the cochlear nucleus coupled with encephalization of the auditory system.

Adult↗
PubMed1983

Effects of age and strain differences on the red nucleus of the mouse mutant Dystonia musculorum.

The mouse mutant Dystonia musculorum exhibits pathological changes in the magnocellular neurons of the red nucleus. The present study shows that allelic differences occur in the age of onset and severity of this pathology. The magnocellular neurons of the Jackson allele (dtJ) almost completely disappear prior to 4 weeks of age while some of these cells are retained in the adult of the Albany strain (dtAlb). However, acetylcholinesterase histochemistry suggests that the remaining rubral neurons in dtAlb are nonfunctional. This pathology may contribute to the severe locomotor disturbances seen in these animals.

Acetylcholinesterase↗
PubMed1983

Neurotoxicity and protein binding of 2,5-hexanedione in the hen.

Previous studies in this laboratory have demonstrated 2,5-dimethylpyrrole adduct formation during in vitro exposure of protein amino groups to the neurotoxic n-hexane metabolite 2,5-hexanedione (2,5-HD). The present investigation reports in vivo pyrrole adduct formation in neural and nonneural protein from 2,5-HD-treated animals. Adult, White-Leghorn hens were given daily doses of either 200 or 70 mg 2,5-HD/kg, po, for up to 55 or 135 days, respectively. Additional animals were given 70 mg/kg for 63 days and then allowed to recover for 72 more days. Protein separation by gel electrophoresis followed by staining with a pyrrole-specific reagent yielded evidence of widespread adduct formation in protein from serum, liver, kidney, brain, and purified myelin. Binding was particularly strong in serum albumin nd myelin basic protein. Quantitation of the adduct in these tissues revealed that its formation reached peak levels at 20 days in high dose and 30 days in low-dose animals. Levels subsequently declined, suggesting the presence of a clearance mechanism capable of removing altered protein during continuing 2,5-HD exposure. Protein from animals on the recovery regimen contained no detectable pyrrole adduct. Pyrrole adduct formation was also detected in neurofilament protein preparations, although protein yields were too low to allow assessment of clearance. Hens at both dosages displayed clinical signs indicative of CNS and PNS neuropathy. Histologic findings included axonal swelling and degeneration in peripheral nerve and some spinal cord nerve tracts. A hypothesis is proposed involving differential clearance of pyrrole adduct from neural vs nonneural tissue to explain the mechanism of action and target organ specificity of 2,5-hexanedione.

Animals↗
PubMed1980

Ascending pathways from the monkey superior colliculus: an autoradiographic analysis.

The autoradiographic tracing method has been used to analyze the distribution of ascending tectofugal pathways in the rhesus monkey. Our findings show that axons which arise from deep collicular neurons terminate within several dorsal thalamic nuclei which in turn project upon the frontal eye fields (area 8) and the inferior parietal lobule (area 7). Both of these cortical areas are functionally quite similar to the deep colliculus, and we suggest that ascending channels from the deep tectum must account, at least in part, for these functional similarities. The present autoradiographs reveal projections to several nuclear zones previously not identified as deep collicular targets in the monkey. Such targets include the visceral cell columns of the oculomotor complex, the rostral interstitial nucleus of the medial longitudinal fasciculus, and the magnocellular division of the ventral anterior nucleus. Deep tectal input also has been shown to terminate quite extensively within the paralamellar region of the mediodorsal nucleus and in the parafascicular nucleus; very little input to the central lateral and centromedian nuclei was observed. Radioisotope injections restricted to the superficial layers reveal dense projections to the parabigeminal nucleus, the pretectum, the inferior and lateral pulvinar nuclei, and to the ventral and dorsal lateral geniculate nuclei. Transported protein within the dorsal lateral geniculate nucleus occupied the "S" layers and the interlaminar zones.

Animals↗
PubMed1980

Sequential auditory and visual discriminations after temporal lobe ablation in monkeys.

Studies in the monkey have shown that cortex outside of the primary projection areas in the superior temporal gyrus and in the inferotemporal region in important for the execution of some auditory and visual descriminations. In this study, six monkeys were trained to perform four auditory and two visual discriminations. Retention tests were given prior to bilateral removal of the anterior part of the lateral surface of the superior temporal gyrus, the inferotemporal region, or both areas together. Superior temporal ablations elicited severe deficits on some auditory discriminations. Inferotemporal ablations caused little or no impairment on visual discriminations. This negative finding is attributed to the sequential rather than spatial mode of presentation of visual stimuli, and to overtraining. A single monkey trained on a spatial visual pattern problem without overtraining was impaired. Another monkey tranied to perform an auditory reverse intensity discrimination exhibited a deficit in ability to perform the problem after removal of auditory cortex within the lateral fissure.

Animals↗
PubMed1979

An autoradiographic study of the rubroolivary tract in the rhesus monkey.

Autoradiographic tracing methods were employed to study the course and distribution of the rubroolivary tract following unilateral injections of tritiated leucine into the rostral red nucleus of seven rhesus monkeys. A topographic organization of projections to the ipsilateral principal nucleus of the inferior olivary complex was demonstrated. Lateral and medial portions of the rostral red nucleus projected to medial parts of the dorsal and ventral laminae of the principal inferior olive respectively; neurons in intermediate lateralities emitted fibers which terminated in lateral parts of the principal olive. Injections involving the oral end of the rostral red nucleus elicited label overlying the medial accessory olive in addition to the principal nucleus. Projections to the medial accessory olive may have arisen from the rostral end of the red nucleus and/or the immediately adjacent tegmentum. There were no projections to the dorsal accessory olive. Fibers of rubral origin also were distributed ipsilaterally to several reticular nuclei including the pedunculopontine, pontis oralis, caudalis, and gigantocellularis.

Animals↗
PubMed1977

An experimental study of the efferent connections of the superior cerebellar peduncle in the rhesus monkey.

Unilateral electrolytic lesions were made in the right superior cerebellar peduncle immediately lateral of its decussation or in the dentate nucleus of 6 monkeys. The course of the contralateral ascending and descending degenerated fibers and sites of preterminal degenerated fibers were studied in material stained by Fink-Heimer, Nissl and Weil methods. Major thalamic sites of preterminal degeneration were in the rostral part of VPLo, and in VPI, VLo, VApc, CL and PCn. In other thalamic nuclei or subdivisions, no preterminal was observed or was questionable. No degenerated fibers entered the internal capsule or corpus striatum. There was abundant preterminal degeneration in the rostral part of the nucleus ruber and adjacent reticular formation. The descending degenerated fibers of the superior cerebellar peduncle led to massive preterminal degeneration in the central part of the nucleus reticularis tegmentalis and in nuclei raphe pontis and magnus. The most caudal site of preterminal degeneration (minimal) was in the nucleus reticularis gigantocellularis adjacent to the median longitudinal fasciculus.

Animals↗
PubMed1977

Second order auditory pathways in the chimpanzee.

Substantial portions of the dorsal, and almost the entire posteroventral and anteroventral (Av) cochlear nuclei were aspirated unilaterally in a chimpanzee. Axonal degeneration was studied by the Fink-Heimer method. The greatest amount of degeneration was followed medially from the region of Av into the lateral part of the trapezoid body. Degeneration also coursed around the superior surface of the restiform body and was traced into the dorsal and intermediate acoustic striae. Within the superior olivary complex, degeneration was distributed to: the ipsilateral lateral superior olive; laterally and medially oriented dendrites of the ipsilateral and contralateral medial superior olivary nuclei respectively (some perisomatic degeneration also was present bilaterally); the contralateral medial trapezoid nucleus; retro-olivary and preolivary cell groups bilaterally. Abundant degeneration passed into the contralateral lateral lemniscus and was distributed largely to its ventral nucleus. The contralateral central nucleus of the inferior colliculus was a major site of termination of ascending second order auditory fibers. The caudal tip of the ipsilateral ventral nucleus of the lateral lemniscus received abundant degeneration, but this diminished rostrally. The ipsilateral inferior colliculus contained a moderate amount of degeneration. A fair number of degenerated second order auditory fibers ascended in the contralateral brachium of the inferior colliculus and were distributed both to the principle and magnocellular divisions of the medial geniculate body. This pathway appears to represent a phylogenetic advance in the brain of the great ape.

Animals↗
PubMed1976

An autoradiographic analysis of the tecto-olivary projection in primates.

Autoradiographic tracing methods were used to demonstrate a well-defined projection from the superior colliculus to the inferior olivary complex in the monkey. This projection originates within the deep layers of the superior colliculus, descends within the contralateral tecto-spinal tract, and terminates within the caudal 1/3 of the medial accessory nucleus. The terminal field is restricted to a densely packed, darkly stained group of cells located in the most dorsal segment of subnucleus b. In one animal, another group of olivary afferents was identified. These fibers also descend within the contralateral tecto-spinal tract, and terminate within the dorsal cap of Kooy. While it was not possible to determine the origin of this projection, our data suggest that it arises within a region adjacent to the rostral pole of the superior colliculus. The present study further indicates that in the monkey relatively few axons which course within the classical tecto-spinal tract pass caudal to the medulla.

Afferent Pathways↗
PubMed1976

Anatomical aspects of the superior olivary complex.

The cytology of the superior olivary complex was studied in nissl stained sections of eight human brainstems, including adult, infant and fetus, and in the brains of ten juvenile rhesus monkeys. The most prominent components of the superior olivary complex of primates were specifically investigated, i.e. the medial (SOM) and lateral (SOL) superior olivary nuclei. Cell counts of these segments were done in human brainstems. The adult SOM was comprised of an average of 11,428 (7,850--15,010) perikarya; the SOL contained an average of 3,923 (2,890--5,400) neurons. These findings indicate that the SOL contains as many cells as reported in other primates, and is not reduced. The SOL appears somewhat inconspicuous in the human because it is organized into as many as six clusters of cells rather than forming one well circumscribed configuration as in the monkey and cat. The total cell population of the SOM together with the SOL was approximately the same on each side of individual brains. If one segment was larger on one side than the opposite side, the other segment was correspondingly reduced to maintain the relative symmetry. This suggests that a single mechanism controls the cell complement of at least two segments of the superior olivary complex.

Adult↗