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A E Hendrickson

Publications and source records attributed to A E Hendrickson.

At least 55 records · Page 3Linked to original sources
PubMed1987

Stratified distribution of synapses in the inner plexiform layer of primate retina.

Distributions of bipolar (B) and amacrine (A) synapses and postsynaptic ganglion cell (G) dendritic profiles in the inner plexiform layer (IPL) were analyzed in EM montages of monkey central and human foveal and peripheral retinae. Synapses and profiles were counted and plotted for each 5% interval of IPL, with 0% at the inner edge of the inner nuclear layer and 100% at the outer edge of the ganglion cell layer. In monkey and human retinae, both A and B synapses occur throughout the IPL, but the ratio of A to B synapses varies from 2:1 to more than 6:1. In the monkey central retina, four bands of A conventional synapses are concentrated at 15, 35, 60, and 80% depth. In the human foveal slope, there are two main A bands at 45 and 85%, whereas in the human periphery, there are five bands at 15, 35, 60, 75, and 90%. In both species, A processes containing large dense-core vesicles are concentrated in three bands at 10-20, 50, and 80-90% depth, corresponding to previously described levels of peptides, dopamine, and GABA. B ribbon synapses are distributed fairly evenly throughout the IPL, with a suggestion of four broadly overlapping bands. Most B ribbons are presynaptic to one A and one G (B----A/G). In the human, there are significantly more B dyads with postsynaptic G's (B----A/G, B----G/G) in the fovea (91%) than in the periphery (66%), implying greater A cell processing peripherally. Also in the human, B terminals containing glycogenlike granules are concentrated in the outer half of the IPL, with agranular terminals in the inner half. Our results demonstrate multiple strata containing different types of synaptic contacts in primate IPL.

Animals↗
PubMed1987

Distribution of cones in human and monkey retina: individual variability and radial asymmetry.

The distribution of photoreceptors is known for only one complete human retina and for the cardinal meridians only in the macaque monkey retina. Cones can be mapped in computer-reconstructed whole mounts of human and monkey retina. A 2.9-fold range in maximum cone density in the foveas of young adult human eyes may contribute to individual differences in acuity. Cone distribution is radially asymmetrical about the fovea in both species, as previously described for the distribution of retinal ganglion cells and for lines of visual isosensitivity. Cone density was greater in the nasal than in the temporal peripheral retina, and this nasotemporal asymmetry was more pronounced in monkey than in human retina.

Animals↗
PubMed1987

Immunocytochemical localization of cholecystokinin and glutamic acid decarboxylase during normal development in the prepyriform cortex of rats.

Immunocytochemical localization of specific neurotransmitters in the brain is becoming increasingly important in studies of maturation. We have used the trilaminar prepyriform cortex (PC) of rats to study the distribution, patterns and relative number of cells, fibers and terminals during postnatal development using antisera to cholecystokinin (CCK) and glutamic acid decarboxylase (GAD). Both antisera show distinct patterns of immunoreactivity at birth and subsequent periods of distinct changes in these patterns. CCK immunoreactivity is rare but present at birth mostly in layer II. There is a dramatic increase of CCK-labeled structures between postnatal (PN) days 6 and 9 and between PN 13 and 21. The adult pattern is observed by PN 21 with large numbers of labeled cells in layer II, numerous terminals in layers II and deep I and large immunoreactive fibers in the lateral olfactory tract. At birth GAD-immunoreactive terminals are present mainly in layer I, forming a distinct pattern of superficial and deep bands. Subsequent major changes occur in this pattern between PN 9 and 13 and again between PN 13 and 21. By PN 21 there appears to be a loss in deeper laminae of GAD positive terminals which are possibly replaced by the increasing numbers of CCK terminals in the same sublaminae. The adult pattern of GAD immunoreactivity is established by PN 21 with terminals and a few cells in layer I. Therefore, throughout development of the rat PC, there is a distinct complementary and changing distribution of GAD and CCK. Factors that may influence these changes in immunoreactivity are discussed.

Aging↗
PubMed1987

Local circuit neurons in the rat ventrobasal thalamus--a GABA immunocytochemical study.

The ventrobasal thalamus of seven rats was processed for immunocytochemistry using antisera to glutamate decarboxylase or gamma-aminobutyrate (GABA). Glutamate decarboxylase-stained sections showed a network of stained fibers and terminals but no stained cell bodies. GABA-stained sections had fewer stained fibers and terminals but did show a few stained cell bodies. Cell bodies were especially apparent when carbazole was used for a chromogen for the peroxidase-antiperoxidase visualization. The GABA-stained cells were found to be distributed throughout the ventrobasal complex, to have smaller soma cross-sectional areas than most other cells (81 +/- 34 microns vs 105 +/- 36 microns for all cells) and to make up 0.4 +/- 0.3% of the neuronal population of the ventrobasal complex. Injections of horseradish peroxidase into the somatosensory cortex (SI) retrogradely filled many neurons in the ventrobasal thalamus, but none of these labeled neurons were double labeled with GABA. These results indicate that the GABA-labeled cells probably represent a small population of local circuit neurons in the rat ventrobasal thalamus.

Animals↗
PubMed1987

Interplexiform cells in macaque monkey retina.

The presence of interplexiform cells in primate retina has been disputed, with the dopaminergic interplexiform cell in the New World monkey being the most fully understood. We have examined interplexiform cells in the Old World monkey using immunocytochemistry with the peroxidase-antiperoxidase method of visualization. In several species of macaque retina, two types of interplexiform cells are found. One stains with antisera to tyrosine hydroxylase, a biosynthetic enzyme for dopamine, and the other stains with antisera to gamma aminobutyric acid (GABA). The cell bodies of these two populations of interplexiform cells are located among the amacrine cells in the inner nuclear layer, and they send processes into both the inner and outer plexiform layers. GABA-positive interplexiform processes to the outer plexiform layer arise from the cell body while tyrosine hydroxylase-positive interplexiform processes most often originate from the heavily tyrosine hydroxylase-stained sublamina one of the inner plexiform layer. Cell-body diameter measurements and morphology suggest that these are different neuronal populations.

Animals↗
PubMed1987

Effects of early unilateral blur on the macaque's visual system. II. Anatomical observations.

We studied the effects of early unilateral blur on the anatomical organization of the visual pathways in 8 macaque monkeys. Blur was induced in one eye, beginning 2-14 d after birth, by 0.5% atropine twice a day. Atropinization was stopped at 6-8 months of age, and the animals were studied for anatomy 3-24 months later. The retina and all other eye tissues showed normal histology. In the dorsal lateral geniculate nucleus (LGN), cells in parvocellular layers receiving input from the atropine-treated eye were 9-32% smaller and were more lightly stained than those in layers innervated by the untreated eye. These changes were generally larger in the LGN ipsilateral to the treated eye. LGN cell size changes were absent or much smaller in the magnocellular layers. In the striate cortex, the distribution of the oxidative enzyme cytochrome oxidase (CO) was markedly altered in layer 4C beta. Layer 4C beta is uniformly stained in normal animals, but showed a distinct pattern of alternating high and low CO bands in the atropine-treated animals; the bands of higher CO activity were narrower than the bands of lower activity and had a 857-1050 micron repeat. Fainter banding was seen in layers 4A, 4C alpha, and 6, but the density of the rows of dark CO-stained dots in layer 3 was unaffected. Double-labeling revealed that the narrow dark CO bands were associated with the centers of the ocular dominance columns devoted to the atropine-treated eye. The distribution of 14C-2-deoxyglucose uptake in visual cortex produced by 4.5-9 c/deg spatial frequency stimulation was strongly biased toward the untreated eye. The treated eye could, however, elicit reasonably strong uptake when stimulated with patterns containing lower spatial frequencies. These results suggest that unilateral neonatal blur preferentially affects the parvocellular layers of the LGN and layer 4C beta of striate cortex, which are the portions of the central visual system associated with the processing of information concerning fine spatial detail. These anatomical changes are consistent with the high spatial frequency loss of vision demonstrated behaviorally and electrophysiologically in the atropine eye-driven visual system of these same animals.

Animals↗
PubMed1987

Effects of early unilateral blur on the macaque's visual system. I. Behavioral observations.

We raised 8 macaque monkeys with chronic atropinization of one eye throughout the first 6-10 months after birth. This rearing procedure produces retinal image blur, with the most pronounced contrast attenuation occurring at high spatial frequencies. Measurements of contrast sensitivity were made using behavioral methods in 6 monkeys and evoked potential methods in 2 monkeys. The results showed that this rearing procedure produced long-term deficits in the contrast sensitivity and spatial resolution of the atropinized eye, which were not due to residual losses in accommodative capacity. There was considerable interanimal variation in the magnitude of the effects on visual performance. Similar losses in visual performance are seen in some forms of human amblyopia. Rearing monkeys with chronic instillation of atropine therefore provides a nonhuman primate model for studying the underlying neural mechanisms of anisometropic amblyopia.

Amblyopia↗
PubMed1987

Effects of early unilateral blur on the macaque's visual system. III. Physiological observations.

We studied the properties of visual cortical and lateral geniculate neurons in 5 macaque monkeys raised with the vision of one eye blurred by daily instillation of atropine. This rearing reduced the degree of binocular interaction in striate cortical neurons and caused a modest shift in eye dominance away from the atropine-treated eye. It also led to a difference in the spatial properties of neurons driven by the 2 eyes: neurons driven by the treated eye tended to have lower optimal spatial frequencies, poorer spatial resolution, and lower contrast sensitivity than neurons driven by the untreated eye. Some of the few binocularly driven neurons had receptive fields with sharply different spatial properties in the 2 eyes, with the treated eye's receptive field always having poorer spatial resolution. In striate cortex, the effects on neuronal spatial properties were less marked in layer 4 than in more superficial or deeper layers; there was no difference in the spatial properties of lateral geniculate neurons driven by the 2 eyes. A small sample of extrastriate cortical neurons from a single animal showed effects similar to those seen in striate cortex. The striate cortical changes varied consistently from animal to animal: The less affected animals had no discernible eye dominance shift and relatively small differences in spatial properties between the eyes; the more affected animals had substantial eye dominance shifts and larger interocular spatial differences. These variations were also reflected in, and consistent with, behavioral and anatomical measurements performed in the same monkeys.

Action Potentials↗
PubMed1986

L-glutamate: a neurotransmitter candidate for cone photoreceptors in the monkey retina.

In order to examine whether L-aspartate and L-glutamate are photoreceptor transmitters in monkey retina, we have carried out two different studies: an autoradiographic localization of the high-affinity uptake sites for aspartate (Asp) and glutamate (Glu), and an immunocytochemical localization of the biosynthetic enzyme, L-aspartate aminotransferase (AAT). Our results show that L-Glu is taken up by a sodium-dependent, high-affinity uptake system with a Km = 8 +/- 3.5 X 10(-6) M and a Vmax = 48 +/- 14 X 10(-12) mol/min/mg protein; 3H-L-Glu or 3H-L- and D-Asp are taken up and accumulated by rod somata and inner segments in retinas incubated at 37 degrees C or at ambient temperature; cones accumulate 3H-L-Glu at ambient temperature but not at 37 degrees C. Neither 3H-L-Asp nor D-Asp is accumulated by cones at either temperature; rods and cones show the same labeling pattern irrespective of whether they are located in the central or peripheral retina; and antiserum to AAT preferentially stains the cone somata, inner segments, and synaptic pedicles, while the outer segments are negative. Both foveal and peripheral cones are strongly reactive, but rods show little reactivity. These findings point to the existence of major differences between rods and cones in the uptake and metabolism of L-Asp and L-Glu and are consistent with L-Glu being a cone transmitter in the monkey retina.

Animals↗
PubMed1986

Glutamic acid decarboxylase (GAD) immunocytochemistry of developing rabbit hippocampus.

Immunocytochemical techniques were used to examine the synaptic relations of inhibitory interneurons in the developing rabbit hippocampus. Glutamic acid decarboxylase (GAD), the synthesizing enzyme for the inhibitory neurotransmitter GABA, was found in interneurons of immature (8 d old) as well as mature (30 d old) tissue. GAD-immunoreactivity was seen in somata, dendrites, and axon terminals of interneurons at both ages. Electron-microscopic examination revealed that GAD-positive "terminals" in immature tissue were often not associated with the usual synaptic specializations, but were rather in simple apposition to the "postsynaptic" element. In mature tissue, GAD-positive terminals made symmetric contacts primarily with pyramidal cell somata, initial segments, and proximal dendrites. In addition, GAD-positive terminals synapsed onto both GAD-positive and GAD-negative interneuron profiles.

Animals↗
PubMed1985

Enucleation demonstrates ocular dominance columns in Old World macaque but not in New World squirrel monkey visual cortex.

The effect of monocular enucleation on basophilic and metabolic staining in primary (striate) visual cortex has been compared in Old and New World monkeys. Both species show a 30-40% shrinkage of neurons in the layers of dorsal lateral geniculate nucleus receiving axons from the enucleated eye. In striate cortex Old World macaque monkeys show alternating bands of increased and diminished staining in layers 3, 4 and 6, corresponding to ocular dominance columns. New World squirrel monkeys show staining patterns in all layers which are unchanged from normal cortex, suggesting that New World monkeys lack obvious ocular dominance columns.

Animals↗
PubMed1985

Subcellular distribution of calcium- and calmodulin-dependent myosin light chain phosphorylating activity in rat cerebral cortex.

The subcellular distribution of Ca2+- and calmodulin-dependent myosin light chain phosphorylating activity in rat cerebral cortex was studied. The activity showed a high degree of association to nerve endings (either crude or purified by discontinuous sucrose density gradient centrifugation). After osmotic shock of the nerve endings, the activity was largely membrane associated and could not be released from membranes by freeze-thawing, dilution, 75 mM NaCl or 4 mM EDTA. The association of Ca2+/calmodulin-dependent myosin light chain phosphorylating activity with synaptosomal membranes suggests a role for calcium-dependent myosin phosphorylation in events relating to neurotransmission.

Animals↗
PubMed1984

Anatomical consequences of long-term monocular eyelid closure on lateral geniculate nucleus and striate cortex in squirrel monkey.

The effects of long-term monocular deprivation on the geniculostriate system in squirrel monkeys were studied with neuroanatomical methods. Four neonates were visually deprived by monocular eyelid suture during their first 10 days of life and survived from 9 to 40 months. In the lateral geniculate nucleus (LGN), deprivation resulted in severe cell size changes. Neurons in the deprived laminae were smaller compared to those in the undeprived laminae. Deprivation left the reciprocal connections between LGN and striate cortex intact: After horseradish peroxidase (HRP) injections into striate cortex, retrogradely transported enzyme labeled a wedge of neurons in deprived and undeprived LGN laminae; anterogradely transported HRP filled preterminal and terminal axons in this wedge. Following 3H-proline injections into the deprived eye for transneuronal transport, autoradiography showed in the ipsilateral striate cortex a silver grain distribution over most of layer IVc similar to that in normal squirrel monkeys, except for a small strip in the anterior calcarine fissure. Here, a few, irregularly spaced "patches" of higher grain density occurred deep in layer IVc. Layer IVc of contralateral area 17 was also uniformly labeled over most of its extent, except for a very few and inconspicuous accumulations of slightly increased silver grains. After visual stimulation of the deprived eye, the 14C-2-deoxyglucose method showed in the contralateral striate cortex some alternating "patches" of higher uptake superimposed on the heavy labeling in layer IVc. Layer IVc in the ipsilateral cortex was more uniformly labeled. Regularly spaced arrays of labeled "puffs" in layers II/III were present in both hemispheres. Cytochrome oxidase staining showed no change in the distribution pattern of the enzyme in the deprived monkeys from the basic pattern of normal adults. No changes in cell sizes were found in layer IVc in cresyl-violet-acetate-stained sections. These results lead to the conclusion that in area 17 of squirrel monkeys there is no distinct segregation of inputs from the two eyes into anatomically discrete ocular dominance columns and they support the view of a predominantly binocular organization of area 17.

Animals↗
PubMed1984

The morphological development of the human fovea.

The development of the human fovea has been traced from 22 weeks gestation to 45 months postpartum using aldehyde-fixed, plastic embedded, serially-sectioned normal retinas. Five anatomical indicators of foveal maturity were used in this study: the shape of the foveal curvatures; the presence of the transient layer of Chievitz; the width of rod-free zone in the central retina; the width and length of the individual foveal cones; and the number and thickness of layers of nuclei within the fovea. The future fovea is identifiable at 22 weeks by the presence of a thick layer of ganglion cells and a photoreceptor layer containing only cones. By 1 week after birth, there is a shallow foveal depression, but the thick cones still lack outer segments and are only 1 cell deep in the fovea. The inner nuclear layer contains a thick transient layer of Chievitz. As judged by these anatomical criteria and compared to normal adult foveas similarly processed, the human fovea reaches maturity between 15 and 45 months of age.

Adolescent↗
PubMed1983

Autosomal recessive eye and brain anomalies: Warburg syndrome.

Two siblings are reported who appear to have an autosomal recessive disorder of eye and central nervous system anomalies. The findings in fourteen previously described and similarly affected patients are summarized. Ocular anomalies include microphthalmos, megalocornea, the Peter anomaly, cataract, coloboma, persistent hyperplastic primary vitreous, and retinal detachment with retinal dysplasia. Central nervous system malformations include agyria-pachygyria, cerebellar dysplasia, encephalocele, Dandy-Walker cyst, and hydrocephalus. We suggest that this disorder be known as Warburg syndrome.

Brain↗
PubMed1983

Background and stimulus-induced patterns of high metabolic activity in the visual cortex (area 17) of the squirrel and macaque monkey.

We have used 2-deoxy-D-[14C]glucose (2-DG) autoradiography and cytochrome oxidase histochemistry to examine background and stimulus-induced patterns of metabolic activity in monkey striate cortex. In squirrel monkeys (Saimiri sciureus) that binocularly or monocularly viewed diffuse white light or binocularly viewed bars of many orientations and spatial frequencies, 2-DG consumption was not uniform across the cortex but consisted of regularly spaced radial zones of high uptake. The zones extended through all laminae except IVc beta and, when viewed tangentially, formed separate patches 500 microns apart. The cytochrome oxidase stain in these animals also revealed patches of high metabolism which coincided with the 2-DG patches. Squirrel monkeys binocularly viewing vertical stripes showed parallel bands of increased 2-DG uptake in the cortex, while the cytochrome label in these animals remained patchy. When monkeys were kept in the dark during 2-DG exposure, 2-DG-labeled patches were not seen but cytochrome oxidase-positive patches remained. In macaque (Macaca nemestrina) monkeys, binocular stimulation with many orientations and spatial frequencies produced radial zones of high 2-DG uptake in layers I to IVa and VI. When viewed tangentially, these zones formed a dots-in-rows pattern with a spacing of 350 X 500 microns; cytochrome oxidase staining produced an identical pattern. Macaca differed from Saimiri in that monocular stimulation labeled alternate rows. These results indicate that there are radial zones of high background metabolism across squirrel and macaque monkey striate cortex. In Saimiri these zones do not appear to be related to an eye dominance system, while in Macaca they do. The presence of these zones of high metabolism may complicate the interpretation of 2-DG autoradiographs that result from specific visual stimuli.

Animals↗