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J F Smiley

Publications and source records attributed to J F Smiley.

At least 19 recordsLinked to original sources
PubMed2001

Somatosensory input to auditory association cortex in the macaque monkey.

We investigated the convergence of somatosensory and auditory inputs in within subregions of macaque auditory cortex. Laminar current source density and multiunit activity profiles were sampled with linear array multielectrodes during penetrations of the posterior superior temporal plane in three macaque monkeys. At each recording site, auditory responses to binaural clicks, pure tones, and band-passed noise, all presented by earphones, were compared with somatosensory responses evoked by contralateral median nerve stimulation. Subjects were awake but were not required to discriminate the stimuli. Borders between A1 and surrounding belt regions were identified by mapping best frequency and stimulus preferences and by subsequent histological analysis. Regions immediately caudomedial to A1 had robust somatosensory responses co-represented with auditory responses. In these regions, both somatosensory and auditory response profiles had "feedforward" patterns; initial excitation beginning in Lamina 4 and spreading to extragranular laminae. Auditory and somatosensory responses displayed a high degree of temporal overlap. Anatomical reconstruction indicated that the somatosensory input region includes, but may not be restricted to, the caudomedial auditory association cortex. As was earlier reported for this region, auditory frequency tuning curves were broad and band-passed noise responses were larger than pure tone responses. No somatosensory responses were observed in A1. These findings suggest a potential neural substrate for multisensory integration at an early stage of auditory cortical processing.

Action Potentials↗
PubMed2000

Nitric oxide synthase interneurons in the monkey cerebral cortex are subsets of the somatostatin, neuropeptide Y, and calbindin cells.

99%) immunoreactive for somatostatin and neuropeptide Y, but did not express calbindin. The LNOS cells comprised about 30% of the somatostatin cells and about 60% of the neuropeptide Y cells. The SNOS cells were nearly always (87-98%) calbindin-immunoreactive, and were rarely or never labeled with antibodies to somatostatin or neuropeptide Y. The SNOS cells accounted for about 20% of all of the calbindin cells. The findings demonstrate that the two types of nNOS cells can be distinguished by antibodies to calbindin, somatostatin and neuropeptide Y, but none of these markers is found exclusively in nNOS cells. Nevertheless, neuropeptide Y-immunoreactivity provides a useful marker for LNOS cells, because it is very dense in these cells and only light in the interneurons that lack nNOS.

Animals↗
PubMed1999

A new molecular link between the fibrillar and granulovacuolar lesions of Alzheimer's disease.

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder involving select neurons of the hippocampus, neocortex, and other regions of the brain. Markers of end stage disease include fibrillar lesions, which accumulate hyperphosphorylated tau protein polymerized into filaments, and granulovacuolar lesions, which appear primarily within the hippocampus. The mechanism by which only select populations of neurons develop these lesions as well as the relationship between them is unknown. To address these questions, we have turned to AD tissue to search for enzymes specifically involved in tau hyperphosphorylation. Recently, we showed that the principal phosphotransferases associated with AD brain-derived tau filaments are members of the casein kinase-1 (CK1) family of protein kinases. Here we report the distribution of three CK1 isoforms (Ckialpha, Ckidelta, and Ckiepsilon) in AD and control brains using immunohistochemistry and Western analysis. In addition to colocalizing with elements of the fibrillar pathology, CK1 is found within the matrix of granulovacuolar degeneration bodies. Furthermore, levels of all CK1 isoforms are elevated in the CA1 region of AD hippocampus relative to controls, with one isoform, Ckidelta, being elevated >30-fold. We propose that overexpression of this protein kinase family plays a key role in the hyperphosphorylation of tau and in the formation of AD-related pathology.

Aged↗
PubMed1999

Cholinergic neurons of the nucleus basalis of Meynert receive cholinergic, catecholaminergic and GABAergic synapses: an electron microscopic investigation in the monkey.

An electron microscopic analysis of the nucleus basalis in the macaque monkey was carried out following the immunohistochemical labeling of choline acetyltransferase, either by itself or in conjunction with glutamate decarboxylase or tyrosine hydroxylase. Cholinergic axon varicosities were frequently encountered, and formed large, usually asymmetric, synapses on both choline acetyltransferase-immunopositive and -immunonegative dendrites of nucleus basalis neurons. Catecholaminergic (tyrosine hydroxylase-immunoreactive) axon varicosities formed synapses which in most cases were classified as asymmetric, and glutamate decarboxylase-immunoreactive (GABAergic) axons formed clearly symmetric synapses, each on to choline acetyltransferase-immunopositive or -immunonegative dendrites. These findings indicate that cholinergic cells in the nucleus basalis of the monkey, also known as Ch4 neurons, receive numerous synaptic inputs from cholinergic, catecholaminergic and GABAergic axons.

Animals↗
PubMed1999

m2 muscarinic receptor immunolocalization in cholinergic cells of the monkey basal forebrain and striatum.

Pharmacological studies have suggested that the m2 muscarinic receptor functions as an autoreceptor in the cholinergic axons which innervate the cerebral cortex and striatum. To test this hypothesis in the macaque monkey, we used a subtype-specific antibody to the m2 muscarinic receptor. Immunoreactive cells were well visualized in the nucleus basalis, where some of these cells displayed dense m2 immunoreactivity, while others were lightly labeled. This heterogeneity of labeling intensity was not based on peculiarities of the methodology, because cholinergic cells of the striatum expressed uniformly dense m2 immunoreactivity. Concurrent labeling with choline acetyltransferase immunoreactivity proved that most of the heavily m2-labeled cells in the nucleus basalis were also choline acetyl-transferase positive. The findings demonstrate that at least 10-25% of the cholinergic neurons in the nucleus basalis of the monkey are densely m2 immunoreactive. In the striatum, concurrent labeling demonstrated that the majority, if not all, choline acetyltransferase-positive cells also contained m2 immunoreactivity. In addition, these experiments identified a population of smaller striatal cells which were m2 immunoreactive and choline acetyltransferase negative. Consecutive labeling with m2 immunoreactivity and NADPH-diaphorase histochemistry demonstrated that many of these m2-immunoreactive non-cholinergic neurons belonged to the population of nitric oxide-synthesizing medium aspiny neurons. The findings indicate that the m2 muscarinic receptor may be expressed at high levels in only a subset of cholinergic basal forebrain neurons. In contrast, m2 receptors appear to be expressed by all cholinergic cells of the striatum.

Animals↗
PubMed1999

Monoaminergic-cholinergic interactions in the primate basal forebrain.

Anatomical studies in the rat have shown that the cholinergic cells of the nucleus basalis receive synapses from monoamine axons, but similar evidence is lacking in primates. We used single- and double-labeling immunocytochemistry to visualize monoamine axons and their relationship with the cholinergic cells of the basal forebrain of the monkey. Norepinephrine axons, labeled with dopamine-beta-hydroxylase antibodies, formed a bed of fine varicose axons that co-distributed with the cholinergic cells. Tyrosine hydroxylase-immunoreactive axons, presumed to be mainly dopaminergic, were 10-20 times more abundant than dopamine-beta-hydroxylase axons throughout the basal forebrain, except in the medial septal area, where their density was lower. Serotonin-immunoreactive axons formed a dense axon plexus throughout the basal forebrain. Double-labeling light microscopy demonstrated that each of the three types of monoamine axons formed frequent direct contacts with the cholinergic cells. Electron microscopy showed that the noradrenergic and the putative dopaminergic axons synapsed on the cholinergic cells. In the human brain, immunolabeling with antibodies to dopamine-beta-hydroxylase, tyrosine hydroxylase and tryptophan hydroxylase (for serotonin axons) showed axon densities in the nucleus basalis comparable to those of the monkey brain. The data demonstrate that all three of these monoamine systems innervate the cholinergic and possibly also the non-cholinergic cells of the nucleus basalis, and therefore affect the release of acetylcholine in the cerebral cortex.

Animals↗
PubMed1998

Infracortical interstitial cells concurrently expressing m2-muscarinic receptors, acetylcholinesterase and nicotinamide adenine dinucleotide phosphate-diaphorase in the human and monkey cerebral cortex.

Intense immunoreactivity for the m2-muscarinic receptor was found in a population of interstitial polymorphic neurons embedded within the infracortical white matter and the adjacent deep layers of the cerebral cortex. These infracortical neurons were evenly distributed throughout architectonic subdivisions of the monkey cortex except for parts of primary visual cortex where they were less numerous. A similar set of m2-immunoreactive interstitial cells was also detected in the human lateral temporal neocortex obtained at surgery. Upon electron microscopic examination, they were found to receive unlabelled synaptic inputs and displayed abundant rough endoplasmic reticulum, a prominent nucleolus, and invaginations of the nuclear membrane. Double labelling of m2 immunoreactivity and acetylcholinesterase histochemistry demonstrated that approximately 90% of the m2-positive infracortical cells were acetylcholinesterase-rich in the monkey and human brains. Conversely, the proportion of acetylcholinesterase-rich infracortical neurons that were m2-immunoreactive was over 90% in the monkey and at least 50% in the human. The concurrent visualization of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) enzyme activity with m2 immunoreactivity in the monkey and human brain showed that 85-95% of m2-immunoreactive infracortical cells were NADPH-d positive. Conversely, about 70% of NADPH-d cells contained m2 immunoreactivity. These observations provide the most convincing information to date that many of the acetylcholinesterase-rich neurons located in the infracortical white matter of the cerebral cortex are likely to be cholinoceptive. The expression of NADPH-d by these neurons suggests that they may also provide a relay through which cholinergic innervation, originating predominantly from the nucleus basalis of Meynert, could regulate the release of nitric oxide in the cerebral cortex and subjacent white matter. The degeneration of these neurons may account for at least some of the depletion of m2 receptors that has been reported in Alzheimer's disease.

Acetylcholinesterase↗
PubMed1997

Butyrylcholinesterase in the life cycle of amyloid plaques.

Deposits of diffuse beta-amyloid (Abeta) may exist in the brain for many years before leading to neuritic degeneration and dementia. The factors that contribute to the putative transformation of the Abeta amyloid from a relatively inert to a pathogenic state remain unknown and may involve interactions with additional plaque constituents. Matching brain sections from 2 demented and 4 nondemented subjects were processed for the demonstration of Abeta immunoreactivity, butyrylcholinesterase (BChE) enzyme activity, and thioflavine S binding. Additional sections were processed for the concurrent demonstration of two or three of these markers. A comparative analysis of multiple cytoarchitectonic areas processed with each of these markers indicated that Abeta plaque deposits are likely to undergo three stages of maturation, ie, a "diffuse" thioflavine S-negative stage, a thioflavine S-positive (ie, compact) but nonneuritic stage, and a compact neuritic stage. A multiregional analysis showed that BChE-positive plaques were not found in cytoarchitectonic areas or cortical layers that contained only the thioflavine S-negative, diffuse type of Abeta plaques. The BChE-positive plaques were found only in areas containing thioflavine S-positive compact plaques, both neuritic and nonneuritic. Within such areas, almost all (>98%) BChE-containing plaques bound thioflavine S, and almost all (93%) thioflavine S plaques contained BChE. These results suggest that BChE becomes associated with amyloid plaques at approximately the same time that the Abeta deposit assumes a compact beta-pleated conformation. BChE may therefore participate in the transformation of Abeta from an initially benign form to an eventually malignant form associated with neuritic tissue degeneration and clinical dementia.

Aged↗
PubMed1997

Cholinergic synapses in human cerebral cortex: an ultrastructural study in serial sections.

Cholinergic axons in the human cerebral cortex were analyzed by electron microscopy. Choline acetyltransferase (ChAT) immunoreactivity was used to identify cholinergic axons in samples of anterior temporal lobe removed at surgery. A systematic survey of labeled axon varicosities, visualized in complete serial sections, showed that 67% of all varicosities formed identifiable synaptic specializations. These synapses were usually symmetric and quite small, often present in only one to two serial sections. However, an occasional synapse was asymmetric and larger, seen in five to seven serial sections. The postsynaptic processes at cholinergic synapses were often identified as spiny dendrites or spines. The existence of cholinergic axons in the human cerebral cortex has been demonstrated in numerous studies. Our findings provide the first ultrastructural evidence that these axons make synaptic contact with cortical neurons in the human brain.

Adult↗
PubMed1996

Serotonergic axons in monkey prefrontal cerebral cortex synapse predominantly on interneurons as demonstrated by serial section electron microscopy.

Anatomical approaches were used to describe the distribution, appearance, and synaptic interactions of serotonin (5-HT)-immunoreactive axons in monkey prefrontal cortex. A plexus of 5-HT axons was found throughout the gray matter, with an especially high density in layer I and a slight increase in layer IV. They were strikingly heterogeneous, with a gradient of morphologies ranging from fine and nonvaricose to highly varicose or thick and nonvaricose. Electron microscopy showed that both varicose and nonvaricose axons were typically filled with clear vesicles and less abundant dense core vesicles. A serial section analysis of 5-HT varicosities in layers I, III, and V showed consistent results across layers. Only about 23% of labeled varicosities formed identifiable synapses. These synapses were consistently asymmetric and were 2-5 serial sections (or 0.08-0.38 mu) in diameter. Targets of identified 5-HT synapses were dendritic shafts with the exception of one cell soma. Followed in serial sections, postsynaptic dendrites typically had morphological features of interneurons, i.e. they lacked spines, had a high density of synaptic inputs, and often had a varicose morphology. Only 8% of postsynaptic shafts were classified as pyramidal dendrites. This is in striking contrast to our previous study in this cortex of dopamine axons, which synapsed predominantly on pyramidal dendrites. These are the first results to indicate that interneurons are the major recipient of identifiable 5-HT synapses in the monkey prefrontal cortex.

Animals↗
PubMed1996

Monoamines and acetylcholine in primate cerebral cortex: what anatomy tells us about function.

In primates, cholinergic and monoaminergic axons that innervate the cerebral cortex originate almost exclusively from subcortical nuclei in the brainstem and basal forebrain. These projections are thought to modulate cortical activity during arousal, attention and memory formation. Physiological and anatomical evaluations of these ascending projections suggest that they have overlapping but somewhat distinctive synaptic targets in the cortex. This review compares the anatomical organization of acetylcholine-, dopamine-, norepinephrine-, and serotonin-containing axon systems in the monkey and human cerebral cortex. Analysis of the distributions of axons, receptors, and synapses suggests that each system is likely to have a differential role in modulating cortical function.

Acetylcholine↗
PubMed1995

Regional, cellular, and subcellular variations in the distribution of D1 and D5 dopamine receptors in primate brain.

The pathways governing signal transduction in the mesocortical and nigrostriatal dopamine systems of the brain are of central importance in a variety of drug actions and neurological diseases. We have analyzed the regional, cellular, and subcellular distribution of the closely related D1 and D5 subtypes of dopamine receptors in the cerebral cortex and selected subcortical structures of rhesus monkey using subtype specific antibodies. The distribution of D1 and D5 receptors was highly differentiated in subcortical structures. In the neostriatum, both D1 and to a lesser extent D5 antibodies labeled medium spiny neurons, while only D5 antibodies labeled the large aspiny neurons typical of cholinergic interneurons. In the caudate nucleus, D1 labeling was concentrated in the spines and shafts of projection neurons, whereas D5 antibodies predominantly labeled the shafts, and less commonly, the spines of these cells. The D1 receptor was abundantly expressed in the neuropil of the substantia nigra pars reticulata while the D5 antibodies labeled only a few scattered cell bodies in this structure. Conversely, D5 antibodies labeled cholinergic neurons in the basal forebrain more intensely than D1 antibodies. Within the cerebral cortex and hippocampus, D1 and D5 antibody labeling was prominent in pyramidal cells. Double-label experiments revealed that the two receptors were frequently coexpressed in neurons of both structures. Ultrastructurally, D1 receptors were especially prominent in dendritic spines whereas dendritic shafts were more prominently labeled by the D5 receptor. The anatomical segregation of the D1 and D5 receptors at the subcellular level in cerebral cortex and at the cellular level in subcortical areas suggest that these closely related receptors may be preferentially associated with different circuit elements and may play distinct regulatory roles in synaptic transmission.

Animals↗
PubMed1994

D1 dopamine receptor immunoreactivity in human and monkey cerebral cortex: predominant and extrasynaptic localization in dendritic spines.

Antibodies to the D1 dopamine receptor were used to localize this protein in several areas of human and monkey cerebral cortex with light and electron microscopy. In addition to cell body labeling in monkeys, all areas of humans and monkeys had a neuropil label with a laminar distribution predicted by previous D1 receptor autoradiography studies. Using electron microscopy, this neuropil label was seen in numerous dendritic spines, in dendritic shafts, and in occasional axon terminals. While labeled spines were common, they represented only a subset of all cortical spines. Serial sectioning through labeled spines showed that the diaminobenzidine reaction product was usually not at postsynaptic densities but instead was displaced to the side of the large asymmetric (presumed glutamatergic) synapse. Furthermore, most labeled spines did not receive synapses with dopaminergic features, suggesting that many D1 receptors are at extrasynaptic sites, possibly receiving dopamine via diffusion in the neuropil. Similarly, double labeling failed to reveal D1 labeling at synapses of tyrosine hydroxylase immunoreactive axons. Localization to numerous dendritic spines suggests that a primary role of D1 receptors is modulation of glutamatergic input to cortical pyramidal cells.

Animals↗
PubMed1993

Silver-enhanced diaminobenzidine-sulfide (SEDS): a technique for high-resolution immunoelectron microscopy demonstrated with monoamine immunoreactivity in monkey cerebral cortex and caudate.

A common frustration of immunoelectron microscopy (IEM) is the density of the 3,3'-diaminobenzidine (DAB) label, which obscures intracellular details of labeled structures. To overcome this problem, a silver enhancement protocol was developed which leaves silver deposits on very low levels of DAB. The resulting label is composed of easily visualized punctate silver deposits, localized in processes with little or no detectable DAB. This technique incorporates several modifications into previously described methods for silver enhancement of DAB. The principal innovation is to pretreat the DAB label with sodium sulfide before silver enhancement, which substantially increases the sensitivity of the silver enhancement. In addition, cysteine was used in place of thioglycolic acid to suppress tissue argyrophilia, allowing use of both glutaraldehyde- and paraformaldehyde-fixed tissue without degradation of ultrastructure. We demonstrate this technique with dopamine, norepinephrine (NE), and serotonin (5HT) immunoreactivity in monkey prefrontal cerebral cortex and with dopamine immunoreactivity in the anterior caudate. The punctate label allows essentially unobscured visualization of the intracellular details and cell membranes of these monoamine axons. Whereas 5HT axons formed small asymmetric synapses, dopamine and NE axons typically formed small symmetric synapses with notably subtle membrane specializations. It is likely that these are often obscured by conventional DAB labeling. The use of several preparations indicates that this technique will be useful with a variety of antibodies. It might also provide an attractive alternative to colloidal gold, especially with glutaraldehyde-fixed tissue which is not easily penetrated by gold particles.

3,3'-Diaminobenzidine↗
PubMed1992

Light and electron microscopic characterization of dopamine-immunoreactive axons in human cerebral cortex.

The distribution and synaptic connections of dopamine axons were studied by light and electron microscopy in human cerebral cortex. For this purpose, dopamine immunoreactivity was characterized in apparently normal anteriolateral temporal cortex, which was removed to gain access to the medial temporal lobe during tumor excision or treatment of epilepsy. Nissl sections showed this to be granular neocortex. Dopamine fibers were distributed throughout this cortex, although there were relatively more fibers in layers I-II and in layers V-VIa, compared to layers III-IV and VIb, resulting in a bilaminar pattern of labeling. In all layers, fibers were seen to form numerous varicosities, and to vary in size from thick to very fine. Fibers were relatively straight, sparsely branched and were oriented in various planes within the cortex. However, in layer I, they often ran parallel to the pial surface. In order to analyze the functional interactions of dopamine fibers, individual cortical layers were surveyed for dopamine synapses. These were usually symmetrical (Gray's type II), although 13% of them were asymmetrical. Approximately 60% of dopamine synapses were made with dendritic spines, and 40% with dendritic shafts, and this ratio was similar in all layers. On both spines and shafts, it was common to see dopamine synapses closely apposed to an unlabeled asymmetric input, suggesting a dopamine modulation of excitatory input. Some postsynaptic dendritic shafts had features of pyramidal cells, including formation of spines. Since pyramidal cells are the major type of cortical spiny neuron, they probably represent the main target of dopamine synapses in this cortex. There were also dopamine profiles apposed to membrane densities on unlabeled axon terminals, suggesting another type of synaptic interaction. These findings provide the first documentation of dopamine synapses in the human cortex, and show that they form classical synaptic junctions. The location of these synapses on spines and distal dendrites, and their proximity to asymmetric synapses, suggest a modulatory role on excitatory input to pyramidal cells.

Axons↗
PubMed1992

The anatomy of dopamine in monkey and human prefrontal cortex.

This chapter reviews recent evidence establishing the comparable organization of dopamine afferents and dopaminergic receptors in the human and monkey prefrontal cortex. Light microscopy using a dopamine-specific antibody reveals that the dopamine innervation in the human prefrontal cortex exhibits a distinct bilaminar distribution with dense bands of fibers in the upper and deeper strata of the cortex, closely resembling the patterning of dopamine fibers in the monkey prefrontal cortex. Also, EM-immunohistochemistry has now revealed identical synaptic complexes both in human and monkey. In both species, dopamine axons from symmetric synapses predominantly on the spines of pyramidal cells. In many cases, the same spine is apposed by an asymmetric, putatively excitatory synapse. Finally, both in human and monkey prefrontal cortex, the dopamine D1-specific ligand, 3H-SCH23390, and the D2-specific ligand, H3-raclopride, label binding sites in laminar positions which match the location of the densest dopamine innervation. These results indicate that the organization of the cortical dopamine system is essentially the same in macaque monkey and human and that the nonhuman primate is a suitable animal model for analysis of dopamine function in prefrontal cortex.

Afferent Pathways↗
PubMed1990

Glycinergic contacts in the outer plexiform layer of the Xenopus laevis retina characterized by antibodies to glycine, GABA and glycine receptors.

Electrophysiological experiments have predicted a direct synaptic input from glycinergic interplexiform cells (IPCs) to GABAergic horizontal cells in the Xenopus retina. However, previous ultrastructural studies failed to demonstrate this input. Here, we used three immunocytochemical approaches to investigate this issue. First, double-label postembedding immunocytochemistry with GABA- and glycine-like immunoreactivity (GABA-LI and glycine-LI) was used to study possible interactions of the glycinergic IPC with GABAergic horizontal cells. Processes postsynaptic to glycine-LI IPC terminals in the outer plexiform layer (OPL) fell into two groups, small microtubule-filled processes and larger electron-lucent processes with sparse microtubules and occasional mitochondria. In no case did we find glycine-LI synapses onto GABA-LI cells or processes. Second, pre-embedding immunocytochemistry was used to label GABA-LI cells and processes in the OPL. GABA-LI was sparse in horizontal cell axons and more intense in horizontal cell somas and in small processes. In agreement with our first set of experiments, GABA-LI profiles did not receive input from conventional synapses. Third, we localized glycine-receptor-like immunoreactivity (GlyR-LI) to several types of apparent synapses in the OPL. As expected, it was found at IPC synapses. Unexpectedly, GlyR-LI was also subsynaptic at photoreceptor synapses onto second order neurons, both at ribbon and basal junction type synapses. At least some of the GlyR-LI photoreceptor synapses were from cones. Also, GlyR-LI was apposed to photoreceptors and to unidentified small diameter processes, where no other indication of synaptic input was evident. Because glycine-LI is not found in photoreceptors, we suggest that glycine receptors at photoreceptor synapses are stimulated by glycine that diffuses from other sites, possibly from IPCs. This interpretation is consistent with available physiological studies of glycinergic effects in this retina.

Animals↗