Biomedical subjects

B G Klein

Publications and source records attributed to B G Klein.

32 records · Page 2Linked to original sources

PubMed1987

The structural and functional characteristics of tectospinal neurons in the golden hamster.

Intracellular recording and horseradish peroxidase (HRP) injection techniques were used to delineate the structural and functional characteristics of the superior collicular cells in the hamster, which could be antidromically activated from the first cervical segment of the spinal cord. Thirty-one such neurons were characterized, filled with HRP, and recovered. Complete physiological data were obtained from another 21 tectospinal cells for which anatomical data were sufficient only to define the laminar location of the cell body from which recordings were made. Of the total sample of 52 cells, 7.7% had their somata in the stratum griseum intermediale (SGI), 50% were in the stratum album intermedium (SAI), 36.5% were in the stratum griseum profundum (SGP), and 5.8% were in the stratum album profundum (SAP). The tectospinal cells were fairly uniform morphologically. They had large (27.7 +/- 5.5 microns diameter) cell bodies, which gave rise to an average of 6.7 +/- 1.2 primary dendrites. These were generally smooth and extended up to 500 microns away from the cell body. In many cases, they ascended out of the deep laminae into the stratum opticum (SO) and/or stratum griseum superficiale (SGS). The axons of TS cells averaged 3.4 +/- 0.8 microns in diameter, and they generally coursed radially to the SAP where they curved around the periaqueductal gray and entered the predorsal bundle. These axons often gave rise to collaterals that arborized in the deep laminae of the ipsilateral superior colliculus and subjacent reticular formation. The tectospinal cells were also fairly uniform physiologically. Their average conduction latency was 2.0 +/- 2.3 ms, and this variable had a strong negative correlation (-.81) with axon diameter for the recovered cells. Most (63.5%) of the TS cells were exclusively somatosensory and gave rapidly adapting responses to deflection of vibrissae and/or guard hairs; 7.7% were bimodal (visual-somatosensory); 11.5% had complex (Rhoades et al., '83) somatosensory receptive fields; 1.9% were discharged only by a noxious pinch, and 15.4% were unresponsive. A common feature of all bimodal tectospinal neurons was dendrites that extended at least as far dorsally as the SO. Whereas there were no other clear-cut correlations between the structural and functional characteristics of these tectal neurons, we did note that all of the cells with complex somatosensory receptive fields received inhibitory input from axons that either originated from, or passed through, the contralateral superior colliculus.

Animals↗

PubMed1987

Renewed growth of identified brainstem axons into fetal cortical transplants in adult rat.

Transplantation of fetal neocortex into the site of trigeminal brainstem injury induces regeneration of trigeminal primary afferent axons in adult rats. Renewed growth of injured primary afferent fibers into donor cortex can be extensive, though the innervation pattern does not resemble that normally seen in either brainstem or somatosensory cortex. Examination of the structural and functional characteristics of individual regenerate axon collaterals suggests that their morphology is determined by both intrinsic and postsynaptic target factors. Marked topographic alterations, however, question the utility of fetal cortical transplantation procedures in effecting functional recovery from brainstem injury.

Animals↗

PubMed1987

Effects of altered visual input upon the development of the visual and somatosensory representations in the hamster's superior colliculus.

The right superior colliculus and right eye were ablated in hamsters within 12 h of birth and the visual and somatosensory representations in the remaining (left) superior colliculus were evaluated using standard single unit recording and receptive field mapping techniques when the animals reached adulthood (at least 3 months of age). In a number of the hamsters used for recording, injections of [3H]leucine were made into the left eye 6-10 days prior to the terminal experiment. This was done to insure that the neonatal lesions did, in fact, produce the extensive recrossing of retinal fibers demonstrated by others who have employed this preparation. All of the hamsters which received [3H]leucine injections prior to the recording experiment exhibited a markedly expanded ipsilateral retinocollicular projection and retinal axons which recrossed the midline at the level of the tectum. The recording experiments showed further that this projection resulted in a visual map which was generally mirror symmetric to that in normal hamsters. There were, however, numerous irregularities and discontinuities in this representation and, in a few hamsters, it appeared almost completely disorganized. There were also a number of abnormalities in the somatosensory representation in the deep tectal laminae of the neonatally brain damaged hamsters. There was a substantial increase in the number of cells with receptive fields that extended onto the ipsilateral side of the body, neurons with split receptive fields were recorded and there were changes in the magnification of different portions of the body surface. These alterations did not, however, change the organization of the somatosensory map in a manner which brought it into alignment with the visual representation in the superficial laminae. Nevertheless, additional recording experiments in animals subjected to enucleation of both eyes and ablation of the superficial laminae of one superior colliculus did indicate that the existence of the aberrant retinal projection was a necessary condition for the somatosensory abnormalities which we observed. Additional anterograde and retrograde tracing experiments demonstrated only one abnormality in the organization of the somatosensory afferent input to the remaining colliculus. In 75% of the brain damaged hamsters, there was a weak crossed projection from the sensorimotor cortex that was never observed in normal animals. Ablation of this cortex at the time of the recording experiment did not, however, reduce the incidence of abnormal somatosensory receptive fields in these hamsters.

Afferent Pathways↗

PubMed1987

Reorganization of the peripheral projections of the trigeminal ganglion following neonatal transection of the infraorbital nerve.

Two different anatomical techniques were used to obtain evidence that transection of the infraorbital (IO) nerve on the day of birth would result in reorganization of the peripheral projections of the trigeminal nerve. In 14 of 19 neonatally nerve-damaged adult rats, injection of horseradish peroxidase (HRP) directly into the IO nerve, proximal to the point of the neonatal transection, resulted in labeled cells in the ophthalmic-maxillary portion of the ganglion and labeled fibers in mandibular sensory nerves. In an additional 28 neonatally nerve-damaged adult rats, double-labeling techniques were employed to document the reorganization suggested by the HRP tracing experiments. In these experiments, one fluorescent tracer, diamidino yellow (DY), was injected directly into the regenerate IO nerve, proximal to the point of the neonatal transection; a second tracer, true blue (TB), was deposited into peripheral ophthalmic and/or mandibular fields. These combinations of injections invariably resulted in the demonstration of a small number (46-401) of double-labeled cells that were located in the ophthalmic-maxillary part of the ganglion. Identical combinations of injections in normal adult rats and the intact sides of nerve-damaged animals never produced more than 6 double-labeled cells per ganglion. In two additional series of experiments, sequential double-labeling techniques were employed to demonstrate that the multiply projecting ganglion cells probably arose in at least two ways: (1) development of non-IO projections by ganglion cells that contributed axons to the IO nerve at the time of the lesion; (2) elaboration of IO axon branches by primary afferent neurons that had non-IO projections at the time of the lesion. A final two-stage double-labeling experiment demonstrated that approximately 75% of the ganglion cells that projected to the whisker pad at birth, and survived transection of the IO nerve on the first postnatal day, regenerated axons into this trigeminal branch.

Amidines↗

PubMed1986

Structural and functional characteristics of commissural neurons in the superior colliculus of the hamster.

Intracellular recording and horseradish peroxidase (HRP) injection techniques were employed to delineate the structural and functional properties of superior collicular (SC) neurons in the hamster that were antidromically activated by electrical stimulation of the contralateral tectum. A total of 39 such cells were completely characterized, injected, and recovered. In ten of these, the axonal filling allowed us to reconstruct at least a portion of the terminal arborization in the SC contralateral to the labelled cell. Two of the recovered neurons were located in the stratum griseum superficiale (SGS), three were in the stratum opticum (SO), ten were in the stratum griseum intermediale (SGI), 11 were in the stratum album intermedium (SAI), 11 were in the stratum griseum profundum (SGP) and two were located in the stratum album profundum (SAP). The recovered cells were highly varied in both their morphological and their physiological characteristics. Somal areas ranged between 74 microns2 and 364 microns2, and the sample of recovered neurons included horizontal cells, narrow field vertical cells, and a variety of other multipolar neurons. Over one-third (38.5%) of the recovered cells were unresponsive, 2.6% were exclusively visual, 33.3% responded only to innocuous cutaneous stimuli, 10.2% were bimodal, 7.7% were specifically nociceptive, and 7.7% had complex (Rhoades, Mooney, and Jacquin: J. Neurosci. 3:1342-1354, '83) somatosensory receptive fields. We observed no clear-cut correlations between the structural and functional characteristics of these neurons. The conduction latencies of the commissural SC neurons ranged between 0.8 and 14.0 ms. The most rapidly conducting cells were located in the SGP and SAP. Conduction latency had a significant negative correlation with soma area. Labelled axons, in many cases, had at least one terminal arbor in a portion of the SC that was mirror symmetric with the location of the cell from which it originated. In several cases, however, commissural axons gave off a number of collaterals across the mediolateral extent of the tectum. commissural axonal terminations were visible only in the laminae ventral to the SO. Several commissural SC neurons also had extensive ipsilateral axon collaterals. Both the ipsilateral and commissural axon branches of these cells gave off en passant and terminal swellings.

Animals↗

PubMed1986

Topographic organization of peripheral trigeminal ganglionic projections in newborn rats.

Retrograde transport of fluorescent tracers (true blue and diamidino yellow) was employed to delineate the topography of the peripheral projections of trigeminal ganglion cells in newborn (less than 12 h of age) rats. Identical injections were made in adult animals for comparison. In neonates, both inter- and intradivisional topography of ganglionic projections were adult-like. Neurons which innervated mandibular fields were located posterolaterally while cells with ophthalmic or maxillary projections were restricted to the anteromedial and central parts of the ganglion, respectively. An adult-like topographic representation of the mystacial vibrissae follicles was also evident in the neonates.

Animals↗

PubMed1986

The structural and functional characteristics of striate cortical neurons that innervate the superior colliculus and lateral posterior nucleus in hamster.

Intracellular recording and horseradish peroxidase injection techniques were used to structurally and functionally characterize the striate cortical neurons in hamster that projected to the superior colliculus and/or lateral posterior nucleus of the thalamus. With two exceptions, the receptive field properties and morphological characteristics of the neurons antidromically activated from the colliculus and lateral posterior nucleus were quite similar. Striate corticotectal and striate cortico-lateral posterior neurons generally had non-oriented receptive fields which gave either "on-off' or no responses to flashed stimuli. Only a small number (less than 5%) were orientation selective, but about one-third were directionally selective. Most of the cells preferred movement with an upward component. Most striate corticotectal and cortico-lateral posterior cells responded to a wide range of stimulus velocities and exhibited little spatial summation. With the possible exception of two cells, all the projection neurons we recovered were large lamina V pyramidal cells whose apical dendrites extended to and branched extensively in layer I. All had extensive (in some cases over 1 mm) tangential axon collaterals, primarily in layers V and/or VI. The electrophysiological experiments also demonstrated that some (50% of a sample of 20 cells) corticotectal neurons also sent an axon collateral to the lateral posterior nucleus. Finally, our recordings showed that many (56% of a sample of 27 neurons) cells which could be antidromically activated from the lateral posterior nucleus, but not the superior colliculus had response latencies which exceeded those of almost all the cells which could be antidromically activated from the tectum. Retrograde transport of diamidino yellow and true blue confirmed the electrophysiological result that individual cortical neurons projected to both the superior colliculus and lateral posterior nucleus. These experiments showed that 20% of the striate cortical cells that projected into colliculus also sent an axon collateral to the lateral posterior nucleus.

Animals↗

PubMed1986

Functional consequences of neonatal infraorbital nerve section in rat trigeminal ganglion.

Standard single-unit recording and stimulation techniques were used to assess the topographic organization, receptive field properties, and projections of cells (n = 297) in the ophthalmic-maxillary part of the trigeminal ganglion in 6 normal adult rats and 15 adults with unilateral infraorbital nerve section at birth (cells recorded ipsilateral to lesion: n = 641; cells recorded on the intact side: n = 223). Stimulating electrodes were placed on the central portion of the regenerate infraorbital nerve and in the trigeminal brain stem subnucleus caudalis in 6 nerve-damaged rats and at equivalent points in 5 normal animals. Data from the normal rats and the intact side of the nerve-damaged animals were identical and were considered together. Of these cells, 73.5% had infraorbital receptive fields. Of these, 77.2% were discharged by vibrissa stimulation (43.8% slow-adapt type I, 10.3% slow-adapt type II, 27.6% low-velocity sensitive rapid adapt, 16.8% high-velocity sensitive rapid adapt, and 1.5% noxious-biased), while the rest responded best to guard hair deflection (12.0%), gentle skin indentation (4.5%), or a strong pinch or deep pressure (6.3%). In stereotaxically matched penetrations in ganglia ipsilateral to the neonatal infraorbital nerve lesions, only 40.6% of the cells had infraorbital receptive fields. Of these, only 37.7% responded to vibrissa stimulation (29.8% slow-adapt type I, 1.2% slow-adapt type II, 2.2% low-velocity sensitive rapid adapt, 32.9% high-velocity sensitive rapid adapt, 33.9% noxious). Other infraorbital cells responded best to guard hair deflection (11.9%), gentle skin indentation (10.8%), or a strong pinch or deep pressure (39.6%). An additional 30 cells did not have a detectable receptive field and were identified only by infraorbital and brain-stem shocks. We also recorded cells with unusual infraorbital receptive fields: 9 units responded to more than 1 vibrissa, 4 were activated by both vibrissa and guard hair deflection, 10 had unusually large skin or deep receptive fields, 1 had a split receptive field, and 7 were discharged only by deep pressure to the region of the nerve section. Seven cells with infraorbital receptive fields were not driven by infraorbital shocks, and 2 were not activated by brain-stem shocks. In normal rats, all cells with infraorbital receptive fields were driven by both electrodes. The percentages of receptive field types for noninfraorbital cells were unchanged in ganglia ipsilateral to the damaged nerve.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1985

Representation of whisker follicle intrinsic musculature in the facial motor nucleus of the rat.

Retrograde transport of wheatgerm-agglutinin horseradish peroxidase (WGA-HRP) and fluorescent tracers (true blue-TB, nuclear yellow-NY, and diamidino yellow-DY) from isolated whisker follicles was used to define the somatotopic organization of the facial (VII) motoneurons which innervate the intrinsic follicle muscles. Motoneurons supplying these muscles were restricted almost completely to the lateral (Martin and Lodge, '77) facial subnucleus and the motoneurons which innervated a given follicle were distributed over the entire length of this subnucleus. Cells projecting to dorsal (A-row) follicles were located in the most lateral part of the lateral subnucleus, while those supplying ventral (E-row) follicles were restricted to the medial part of the subnucleus. Injections of different tracers into rostral and caudal follicles within a given row revealed no somatotopic representation of the rostrocaudal axis of the whiskerpad. Additional control experiments demonstrated that some of the labelling obtained with WGA-HRP resulted from spread of this tracer to extrinsic muscles. This was not the case with the fluorescent tracers. The results of the control experiments suggested further that a significant percentage of the motoneurons in the lateral facial subnucleus innervate only intrinsic follicle muscles.

Animals↗

PubMed1985

Extensive recrossing of retinotectal axons after neonatal unilateral superior collicular lesions in hamster.

Anterograde transport methods were used to examine the ipsilateral retinocollicular projections of adult hamsters subjected to ablation of one superior colliculus (SC) on the day of birth. In many of these animals ipsilateral retino-SC axons were not limited to the medial part of the remaining tectum as previously reported but encompassed the entire rostrocaudal and mediolateral extents of this SC. A common pattern was the existence of a dense patch of label contiguous with the midline, a more lateral region of diffuse labeling, a second dense lateral patch and diffuse labeling which extended to the lateral boundary of the tectum. The dense patches of label were usually aligned into rostrocaudally oriented bands. Additional experiments in which one optic tract was sectioned a week prior to the eye injection showed that the reorganization was primarily due to axons which recrossed the midline at the level of the midbrain. However, the uncrossed retinotectal projection was also abnormally dense in the animals subjected to neonatal SC lesions. Dense patches of label in the caudal half of the tectum were only observed when recrossing fibers were labeled. In a final set of experiments, both the ipsilateral and contralateral projections were labeled with different tracers in individual hamsters. These experiments showed a clear tendency for fibers from the two eyes to segregate in the remaining SC. This segregation was, however, incomplete, even in regions where labeling from each eye was quite dense.

Animals↗

PubMed1985

Grasping in the pigeon (Columba livia): final common path mechanisms.

A combination of cinematographic and denervation procedures were used to analyse the mechanisms involved in the adjustment of gape size during grasping in the pigeon. Gape size was found to vary directly with seed size and to reflect the operation of two variables, jaw opening velocity and jaw opening duration. Effects upon duration are mediated, indirectly, by the effect of seed size upon head height, which, in turn, controls the velocity of head descent. The data suggest that the control of gape during grasping may involve two different effector systems (jaw muscles, neck muscles). Analysis of the displacement of individual jaws (maxilla, mandible) during grasping indicates that both opener muscles take part in the control of gape. Denervation experiments (motor nerve section) identified these opener motoneurons as contributors to the final common path for the opening phase of grasping. A comparison of the kinematics of pecking/grasping in pigeons and reaching/grasping in humans reveals a number of similarities in the topography and spatiotemporal organization of these behaviors.

Animals↗

PubMed1985

Correlations between the structural and functional characteristics of neurons in the superficial laminae and the hamster's superior colliculus.

Intracellular recording, receptive field mapping, and horseradish peroxidase (HRP) injection techniques were used to determine the structural and functional characteristics of neurons in the superficial laminae (stratum griseum superficiale and stratum opticum) of the hamster's superior colliculus (SC). Fifty-nine neurons (from 38 different hamsters) were successfully characterized, injected with HRP, and recovered. Of these, 8 were marginal cells, 14 had stellate morphology, 10 had narrow, vertically oriented dendritic trees, 12 had wide, vertically oriented dendritic arbors, and 8 were horizontal cells. Seven neurons had somatodendritic morphologies which did not fall into any of these groups. Overall, the distribution of receptive field properties for these cells matched that obtained in previous extracellular recordings from the superficial SC laminae in this species (Chalupa, L.M., and R.W. Rhoades (1977) J. Physiol. (Lond.) 270: 595-626; Chalupa, L.M. and R.W. Rhoades (1978) J. Physiol. (Lond.) 274: 571-592). There were significant correlations between receptive field properties and morphology. Sixty-four percent of the stellate cells and 75% of the marginal cells were directionally selective. Only 17% of the other cell types exhibited this response property. In addition, only 36% of the stellate cells and 25% of the marginal neurons were discharged by stationary, flashed spots. Eighty-one percent of the other recovered cells gave reliable responses to such stimuli. Stellate and marginal cells could also be differentiated from the other cell types on the basis of speed selectivity. Only 29% of the stellate and 13% of the marginal cells responded to stimulus speeds in excess of 20 degrees/sec.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Dendrites of deep layer, somatosensory superior collicular neurons extend into the superficial laminae.

Intracellular recording and horseradish peroxidase (HRP) injection techniques were used to delineate the structural and functional properties of superior collicular (SC) neurons in hamsters. Of 34 cells recovered from the deep laminae (those ventral to the stratum opticum--SO), 26 were exclusively somatosensory and 10 of these extended dendrites into the superficial layers, the stratum griseum superficiale (SGS) and SO. In 2 instances, dendrites extended only to the SO, but in 8 others they reached the SGS. Three of the latter cells had dendrites which terminated just beneath the pial surface. These findings show that an anatomical substrate for communication from superficial to deep layer cells exists in the hamster SC, but that such communication may not necessarily be reflected in the response of deep layer neurons.

Animals↗

PubMed1982

Afferents to the trigeminal and facial motor nuclei in pigeon (Columba livia L.): central connections of jaw motoneurons.

Trigeminal and facial motor nuclei innervating the pigeon's jaw muscles were identified using a combination of microstimulation and EMG recording and HRP injections were made iontophoretically. The trigeminal motor nucleus receives an ipsilateral projection from sensory neurons in the trigeminal mesencephalic nucleus which forms the afferent limb of the monosynaptic stretch reflex of the jaw-closers. Both the trigeminal and facial motor nuclei receive bilateral projections from interneurons in the intertrigeminal area and the lateral (parvocellular) reticular formation of the pons and medulla. These neurons serve as premotor elements in the control of jaw movements, mediating ascending, descending and internuclear connections. The similarity of inputs to the trigeminal and facial nuclei may reflect their common function as jaw motoneurons in this species.

Afferent Pathways↗