Subjacent White Matter Research Articles

Expression of α 3, β 3 and γ 1 GABA A receptor subunit messenger RNAs in visual cortex and lateral geniculate nucleus of normal and monocularly deprived monkeys

Complementary RNA probes derived from complementary DNA specifically subcloned from monkey tissue were used to localize, by in situ hybridization histochemistry, the relatively rare α 3, β 3 and γ 1 subunit transcripts of the GABA A receptor in visual cortex and lateral geniculate nucleus of normal monkeys and in monkeys that had been deprived of vision in one eye. Overall, levels of α 3, β 3 and γ 1 subunit transcripts were very low. In the primary visual cortex (area 17) they were concentrated in layers II and VI and in a stratum of white matter subjacent to layer VI. The localization and density of the three messenger RNAs closely resembled those of other rare (α 2, α 5 and β 1) transcripts but their distribution also overlapped that of the predominant α 1, β 2 and γ 2 subunit transcripts. In area 18, α 3 and β 3 transcript distribution resembled that in area 17, with the addition of a third band of hybridization in layer IV for β 3. γ 1 subunit transcript localization in area 18 differed significantly from that in area 17, with increased expression restricted to layer IV. In the dorsal lateral geniculate nucleus, β 3 and γ 1 transcripts were expressed at low levels across all layers while α 3 transcripts were restricted to the magnocellular layers. Following 15 and 18 day periods of monocular deprivation, induced by intravitreal injections of tetrodotoxin, levels of α 3 receptor subunit transcripts showed modest reductions in layer VI of area 17 and in deprived geniculate laminae of adult animals. Reductions in α 3 transcript levels were much more pronounced in layer IVCβ of a five-month-old monkey deprived for the same time. Levels of β 3 and γ 1 transcripts were unaffected by monocular deprivation in cortex and geniculate at any age. Taken together with studies of other GABA A receptor transcripts, these results demonstrate the heterogeneity of GABA A receptor messenger RNA expression in the monkey geniculo-striate pathway and the varied response to reduced neuronal activity.

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.

NADPH-diaphorase activity in area 17 of the squirrel monkey visual cortex: neuropil pattern, cell morphology and laminar distribution.

We studied the distribution of NADPH-diaphorase activity in the visual cortex of normal adult New World monkeys (Saimiri sciureus) using the malic enzyme "indirect" method. NADPH-diaphorase neuropil activity had a heterogeneous distribution. In coronal sections, it had a clear laminar pattern that was coincident with Nissl-stained layers. In tangential sections, we observed blobs in supragranular layers of V1 and stripes throughout the entire V2. We quantified and compared the tangential distribution of NADPH-diaphorase and cytochrome oxidase blobs in adjacent sections of the supragranular layers of V1. Although their spatial distributions were rather similar, the two enzymes did not always overlap. The histochemical reaction also revealed two different types of stained cells: a slightly stained subpopulation and a subgroup of deeply stained neurons resembling a Golgi impregnation. These neurons were sparsely spined non-pyramidal cells. Their dendritic arbors were very well stained but their axons were not always evident. In the gray matter, heavily stained neurons showed different dendritic arbor morphologies. However, most of the strongly reactive cells lay in the subjacent white matter, where they presented a more homogenous morphology. Our results demonstrate that the pattern of NADPH-diaphorase activity is similar to that previously described in Old World monkeys.

Neuropeptide Y-like immunoreactivity in area 17 of chimpanzee.

The distribution and morphology of neuropeptide Y-like immunoreactive (NPY+) neurons in area 17 were studied in 4 chimpanzees (15 to 56 years old) with the aid of immunocytochemical methods. The NPY+ neurons were not pyramidal, but were either multipolar, bipolar, or bitufted in shape. They occurred most frequently in layer 6 and the subjacent white matter, they were sparser in the supragranular layers, and were few in layer 4. The NPY+ somata in the supragranular layers were significantly smaller than those in the infragranular layers. The axon of NPY cells originated either from the soma or from the primary dendrite. The distribution and morphology of NPY+ neurons were not different between the youngest and the oldest chimpanzee. The oval shape of NPY+ neurons, however, changed slightly with aging to a more circular shape. The density of NPY+ fibers was laminar-dependent. A distinct plexus extended through the upper part of layer 4 and the lowest aspect of layer 3. A thin fiber band was found in the lowest part of layer 4. Some NPY+ axons vertically traversed the cortex between pia and white matter. In the superficial layers, "snarls" of fibers appeared.

Reduced nicotinamide adenine dinucleotide phosphate-diaphorase/nitric oxide synthase profiles in the human hippocampal formation and perirhinal cortex.

Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d)-stained profiles were evaluated throughout the human hippocampal formation (i.e., dentate gyrus, Ammon's horn, subicular complex, entorhinal cortex) and perirhinal cortex. NADPH-d staining revealed pleomorphic cells, fibers, and blood vessels. Within the entorhinal and the perirhinal cortices, darkly stained (type 1) NADPH-d pyramidal, fusiform, bipolar, and multipolar neurons with extensive dendrites were scattered mainly within deep layers and subjacent white matter. Moderately stained (type 2) NADPH-d round or oval neurons were seen mainly in layers II and III of the entorhinal and perirhinal cortices, in the dentate gyrus polymorphic layer, in the CA fields stratum pyramidal and radiatum, and in the subicular complex. The distribution of type 2 cells was more abundant in the perirhinal cortex compared to the hippocampal formation. Lightly stained (type 3) NADPH-d pyramidal and oval neurons were distributed in CA4, the entorhinal cortex medial subfields, and the amygdalohippocampal transition area. Sections concurrently stained for NADPH-d and nitric oxide synthase (NOS) revealed that all type 1 neurons coexpressed NOS, whereas types 2 and 3 were NOS immunonegative. NADPH-d fibers were heterogeneously distributed within the different regions examined and were frequently in close apposition to reactive blood vessels. The greatest concentration of fibers was in layers III and V-VI of the entorhinal and perirhinal cortices, dentate gyrus polymorphic and molecular layers, and CA1 and CA4. A band of fibers coursing within CA1 divided into dorsal and ventral bundles to reach the presubiculum and entorhinal cortex, respectively. Although the distribution of NADPH-d fibers was conserved across all ages examined (28-98 years), we observed an increase in the density of fiber staining in the aged cases. These results may be relevant to our understanding of selective vulnerability of neuronal systems within the human hippocampal formation in aging and in neurodegenerative diseases.

Symbiosis between in vivo and in vitro NMR spectroscopy: The creatine, N-acetylaspartate, glutamate, and GABA content of the epileptic human brain

High resolution 1H NMR spectroscopy was used to analyze temporal lobe biopsies obtained from patients with epilepsy. Heat-stabilized cerebrum, dialyzed cytosolic macromolecules, and perchloric acid extracts were studied using one- and two dimensional spectroscopy. Anterior temporal lobe neocortex was enriched in GABA, glutamate, alanine, N-acetylaspartate, and creatine. Subjacent white matter was enriched in aspartate, glutamine, and inositol. The N-acetylaspartate/creatine mole ratio was lower in anterior temporal neocortex with mesial (0.66) than neocortical (0.80) temporal lobe epilepsy. Human brain biopsy samples were separated into crude and refined synaptosomes, neuronal cell bodies, and glia using density gradient centrifugation. Neuronal fractions were enriched in glutamate and N-acetylaspartate. Glial cell fractions were enriched in lactate, glutamine, and inositol. The creatine content was the same in biopsied epileptic cortex (8.8–8.9 mmol/kg) and normal in vivo occipital lobe (8.9 mmol/kg). Glutamate content was higher in epileptic cortex at biopsy (10.1–10.5 mmol/kg) than normal in vivo occipital lobe (8.8 mmol/kg). GABA content was higher in biopsies of epileptic cortex (2.3–2.2 mmol/kg) than in normal in vivo occipital lobe (1.2 mmol/kg). N-acetylaspartate content was lower in biopsied epileptic temporal cortex (5.8–6.8 mmol/kg) than normal in vivo occipital lobe (8.9 mmol/kg). Paired in vivo and ex vivo measurements are critical for a firm understanding of the changes seen in the 1H-spectra from patients with epilepsy.

Multiple types of nitrogen monoxide synthase-/NADPH diaphorase-containing neurons in the human cerebral neocortex

Nitrogen monoxide (NO) synthase (NOS)-containing neurons (NOSN) were identified by means of reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry in nine areas of the human cerebral neocortex from patients 9–74 years og age. Labeled neurons were analyzed according to their disposition in the various layers of the cortical gray and immediately subjacent white matter, and classified according to their cytological features. The vast majority of NOSN (about 80%) are situated in the subcortical white matter and not in the cortical gray proper. Nevertheless, these NOSN extend their processes into the cortical gray and thus appear to participate in intracortical circuits, along with the minority of NOSN situated in all cortical layers. Although many NOSN are small aspiny local circuit neurons, as reported previously, additional distinct cytological types of NADPH diaphorase-positive neurons were also identified, including: (a) local circuit neurons in layer I; (b) granule cells in layer II, and (c) non-pyramidal neurons with densely spinous dendrites in the white matter immediately under the cortical gray. Processes fulfilling light microscopic criteria for axons were seen in many of the above cell types originating from proximal dendrites and, less frequently, from a presumed axon hillock. Taken together, these observations indicate that NOSN belong to several distinct morphological and presumably functional classes, some of which have a unique or restricted laminar location, raising the possibility that some of these various classes of neurons may be selectively affected or spared in neurodegenerative disorders.

GABAA receptor subunit immunoreactivity in primate visual cortex: distribution in macaques and humans and regulation by visual input in adulthood

Subunit proteins that make up functional GABAA receptors were localized immunocytochemistry in the primary visual cortex (area 17) of adult monkeys and humans. Immunoreactivity for the alpha 1, beta 2/3, and gamma 2 subunits is greatest in layers (II-III, IVA and IVC) of monkey area 17 that contain the highest density of GABA neurons and terminals. Immunostaining for each subunit is unevenly distributed in layers II and III, where patches of immunoreactivity correspond to regions of intense cytochrome oxidase (CO) staining, and in layer IVA, where intense immunoreactivity forms a honeycomb pattern identical to the CO staining pattern. Immunoreactivity for the subunits is localized principally within the neuropil, which, by simultaneous comparison with the distribution of microtubule-associated protein immunostaining, was found to include bundles of thin dendrites and zones of numerous dendritic segments. In addition, gamma 2 immunostaining surrounds the somata of a subpopulation of GABAergic neurons, immunoreactive for the calcium-binding protein parvalbumin. All three subunits are present in the somata and processes of neurons that occupy the white matter subjacent to monkey area 17. In human visual cortex, the alpha 1, beta 2/3, and gamma 2 subunits are distributed in a manner similar to that found in monkeys, with relatively intense immunostaining in layers IVC and IVA. In layer IVC, vertical stripes of intense receptor immunostaining (20-30 microns wide) alternate with wider stripes of pale immunostaining (30-60 microns wide). In the upper and lower halves of IVC beta, these stripes form lattices similar to those in layers IVC and IVA of monkeys. Following monocular deprivation by intravitreal injections of TTX in adult monkeys, immunoreactivity for each subunit in layer IVC consists of alternating intensely and lightly stained stripes. Comparison with the pattern of CO staining indicates that intense immunostaining for alpha 1, beta 2/3, and gamma 2 occurs in normal-eye stripes while abnormally light immunostaining is present in deprived-eye stripes. For all three subunits, immunoreactivity in deprived-eye stripes is reduced within 5 d of monocular deprivation and remains abnormally low for deprivations that extend to at least 30 d. These findings indicate that each of several GABAA receptor subunits adopt similar laminar and compartmental distributions in monkey and human area 17 and are likely to be expressed by the same neurons. The deprivation-dependent reduction in immunoreactivity for alpha 1, beta 2/3, and gamma 2 subunits suggests that all are regulated by visually driven activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Microglial reaction in Pick's disease

Number and morphology of microglial cells (MC) were compared in 6 cases each of Pick's disease (PD), Alzheimer's disease (AD) and controls using immunohistochemistry with the monoclonal antibody Ki-M1P. The severely involved neocortex of both PD and AD, and in particular the white matter subjacent to spongy PD lesions showed a marked increased of MC density, whereas non-affected PD areas and AD white matter showed no MC changes. The PD hippocampus, particularly the dentate gyrus, showed reduction of MC density and processes. We conclude that (1) MC reaction represents a major element of PD histopathology, and (2) density, morphology and distribution of MC are different in AD and PD.

Neurons Derived from a Human Teratocarcinoma Cell Line Establish Molecular and Structural Polarity Following Transplantation into the Rodent Brain

Studies of neurons grafted into the brains of experimental animals have been limited by the lack of suitably homogeneous populations of neurons for transplantation. Here we describe the transplantation and survival of pure, postmitotic human neurons (NT2N cells) into the rat brain. NT2N cells were derived from a human teratocarcinoma line (NTera2/clone D1 or NT2 cells) in vitro by retinoic acid treatment. Approximately 5-10 × 10 4 NT2N cells (including previously frozen aliquots of NT2N cells) were injected into the neocortex, subjacent white matter, or hippocampus of adult ( N = 51) or neonatal ( N = 17) Sprague-Dawley rats. Cyclosporine (7-10 mg/kg) was administered daily to 13 adult rats for up to 12 weeks post-transplant prior to sacrifice. Untreated rats survived for up to 21 weeks post-transplant. Injection sites were serially sectioned and NT2N grafts were analyzed immunohistochemically using antibodies to diverse neuronal and glial proteins to assess the lineage of the grafted cells and their ability to establish molecular and structural polarity. NT2N cells transplanted into untreated adult and neonatal rat brains were committed exclusively to the neuronal phenotype and survived for as long as 8 weeks, although most were rejected after 4 weeks. However, cyclosporine prolonged survival of the NT2N grafts for up to 12 weeks. Further, grafted NT2N cells exhibited an asymmetric geometry (with long axons and simplified dendrites), as well as molecular polarity (with highly phosphorylated neurofilament proteins segregated in axons and microtubule associated protein 2 confined to perikarya and dendrites) by 4 weeks post-transplant. However, the grafted neurons did not become fully mature as evidenced by their failure to express the most highly phosphorylated heavy neurofilament proteins. Finally, previously frozen NT2N cells survived in the rat brain, and none of the grafts formed neoplasms. We conclude from these studies that transplanted NT2N cells represent a highly advantageous model system for studies of the developmental biology of neurons.

Cortical astrocytosis in juvenile rhesus monkeys infected with simian immunodeficiency virus.

The pattern of expression of GFAP immunoreactivity in astrocytes of the juvenile rhesus monkey cortex was examined following infection with simian immunodeficiency virus (SIV). Blocks of cerebral cortex plus subjacent white matter from saline- and formalin-perfused brain were examined by peroxidase-linked immunochemical and immunofluorescence staining of deparaffinized sections. Strong GFAP immunoreactivity was found in astrocytic cells in both uninfected and SIV-infected juvenile macaque in the subpial cerebral cortex and in subcortical white matter, where GFAP-positive cells were abundant. GFAP staining of cortical layers 2-6 on the other hand was weak or absent in three uninfected controls and one infected animal without cognitive impairment, but moderate to strong in animals productively infected with SIV that demonstrated cognitive and/or motor impairment. These data demonstrate a cortical locus of astrocytic activation in rhesus monkeys infected with primate immunodeficiency virus isolate SIVB670 which, like HIV-1 in man, causes motor/cognitive impairment as well as immunodeficiency disease.

Troubled reaching after right occipito-temporal damage

We encountered a man with an unusual reaching disturbance due to a stroke in the right occipito-temporal cortex and subjacent white matter. We studied his behavior in detail including vision and hand control. He had a left homonymous hemianopia. In his remaining fields static visual acuity and stereoacuity were normal, but he could not detect a coherent motion signal or follow moving targets with smooth pursuit. Transduction of limb movements using an optoelectronic technique showed abnormal morphology, increased variability and markedly prolonged latencies for transport to external visual targets, yet he achieved these targets with precision. Reaching to selfbound targets, and to the remembered locations of external targets with vision blocked was 5 × faster. The findings may be explained by: (1) damage in regions homologous to areas TF and TH in the monkey, which provide visual inputs to hand and forelimb representations in the cortex; (2) injury in human regions homologous to the monkey's MT complex, with inability to use visual information on the movement of the limb due to a visual motion processing defect; and (3) disruption of visual cortical-subcortical connections mediating crucial transformations among limb and target representations.

Cellular generators of the cortical auditory evoked potential initial component

Cellular generators of the initial auditory evoked potential (AEP) component were determined by analyzing laminar profiles of click-evoked AEPs, current source density, and multiple unit activity (MUA) in primary auditory cortex of awake monkeys. The initial AEP component is a surface-negative wave, N8, that peaks at 8–9 msec and inverts in polarity below lamina 4. N8 is generated by a lamina 4 current sink and a deeper current source. Simultaneous MUA is present from lower lamina 3 to the subjacent white matter. Findings indicate that thalamocortical afferents are a generator of N8 and support a role for lamina 4 stellate cells. Relationships to the human AEP are discussed.

A transitory population of substance P-like immunoreactive neurones in the developing cerebral cortex of the mouse

Immunocytochemical methods were used to investigate the developmental expression of substance P (SP) in mouse cerebral cortex. SP-like-immunoreactive cells were first detected at postnatal day 0 (PO), their numbers being notably increased by P2. Immunopositive cells were especially abundant in layer VIb and in the subjacent future white matter, although they were also present in layer V. Between P5 and P8 the number of SP-like-immunoreactive cells gradually decreased, being almost completely absent by P12. At these stages cells were only observed in the deepest cortical layers. From P16 onwards, the adult pattern of SP-like immunoreactivity emerged with a few immunopositive cells scattered throughout the cortical layers. The present data show a transitory population of SP-like-immunoreactive cells present in the mouse cerebral cortex during the first postnatal week. On the basis of close correlations of SP-like expression with the distribution or transitory populations and the timing of cell death in rodents, we propose that most of the SP-like-immunoreactive cells reported here would probably disappear by cell death.

GABA neuronal subpopulations in cat primary auditory cortex: co-localization with calcium binding proteins

GABA immunoreactive neurons are present in all layers of cat AI and in the subjacent white matter; they are most numerous in layer II, the superficial half of layer III and layer IV. Double labeling immunofluorescence reveals that subpopulations of the GABA neurons are immunoreactive for the calcium binding proteins (CaBP), calbindin (28 kDa vitamin D-dependent calcium binding protein) and parvalbumin. Both proteins are present exclusively with GABA neurons but in subpopulations that are entirely separate. The two proteins together are present in approximately 70–75% of the GABA neurons; the largest group of GABA neurons displaying no CaBP immunoreactivity is in layers I–IIIA and VI. Calbindin immunoreactive neurons are present in two bands within cat AI: a superficial band, made up of numerous stained somata and processes, that includes layers II and IIIA and a deeper band, containing fewer neurons, that is coextensive with layer VI. Isolated calbindin somata are scattered between the two bands are very rarely in the subcortical white matter. Parvalbumin immunoreactive neurons are very densely packed in layers IIIB and layer IV, and include the majority of GABA neurons in layer IV; they are also numerous in layer VI. Parvalbumin immunoreactive neurons are much less numerous in layers II, IIIA and V and are absent from layer I. Light microscopic analyses suggest that the two subpopulations of GABA/CaBP neurons include several morphological types. In addition to the intrinsic somata and processes, numerous axons in white matter subjacent to AI are immunoreactive for either or both of the two proteins. These data demonstrate that cat AI is similar to other cortical areas in other species in posessing subpopulations of GABA neurons that express the CaBPs, calbindin and parvalbumin.

Polarity reversal of N20 and P23 somatosensory evoked potentials between scalp and depth recordings

From depth and scalp electrodes, we recorded MN-SSEPs of a 33-year-old man with right parietal dysfunction and refractory right temporal seizures. A depth lead with 8 electrodes was implanted deep in each parietal-temporal region. Stimulation and recording parameters followed American EEG Society guidelines. Scalp recordings had well-defined P9, P13–14, N18, N20, and P23 potentials with normal conduction times bilaterally. Depth recordings showed potentials of greater number, voltage, and coherence. P13–14 and N18 were recorded at all depth sites with latencies similar to those at the scalp. N18 had markedly greater voltage and duration near the thalamus, with multiple fast components on its ascending phase. In the deep parietal region there was a positivity corresponding to the scalp N20 and a negative potential equal in latency to scalp P23. These findings support an origin of P13–14 caudal to the thalamus, multiple thalamic and possibly rostral brain-stem generators for N18, and generation of N20 and P23 in sensory cortex or subjacent white matter.

Synaptic Relationships of Serotonin-Inmmunoreactive Terminal Baskets pm GABA Neurons in the Cat Auditory Cortex

Correlative light and electron microscopic immunocytochemical methods were used to analyze the 5-HT innervation of the primary auditory area (AI) of the cat cerebral cortex and to examine the synaptic relationships of 5-HT basket terminations on target neurons in that area. Three morphological types of 5-HT-immunoreactive fibers are present: type I, which is very thin and very finely beaded; type II, which is thin and coarsely beaded; and type III, which has a relatively thick main shaft and very few beads. Type I is the most abundant, type II is relatively less common, and type III is the least abundant type. The 3 types of fibers are present through the thickness of AI and in the subjacent white matter, but the densest plexus is found in layers I-III. One of the most characteristic features of type II fibers is that they commonly form small, dense clusters that resemble baskets apposed to the somata and primary dendrites of unstained neurons. The basket formations are more frequently found in layers I and II, and they vary in complexity. Simultaneous immunostaining for GABA and 5-HT reveals that many 5-HT baskets surround the somata and dendrites of GABA neurons. In 2-microns-thick plastic sections, each basket formation can be seen surrounding 1 or a group of 2 or 3 cells. In the latter case, one cell is much larger and at the electron microscope level is identified as a neuron, while the other cells are neuroglial cells. Reconstructions were made from serial electron micrographs of 135 5-HT-immunoreactive boutons. Of these boutons, 110 belonged to basket formations, 14 to type I axons located in the neuropil, and the remaining 11 to type II fibers located in the white matter. Only 4 of the 135 boutons made conventional synaptic contacts. These were of the asymmetrical type. Most of the boutons made very small, indistinct membrane specializations or none at all. The present results therefore suggest a strong interaction between 5-HT axon terminals and specific GABA neurons, which may be mediated by release sites that are not associated with morphologically distinct synaptic contacts.

Morphological Estimation of Brain Extracellular Fluid Dynamics in Cold‐induced Edema from the Aspect of Cerebrospinal Fluid‐Extracellular Fluid Communication

Following the induction of cold injury in the parietal cortex of rats, the brain extracellular fluid dynamics under conditions of cryogenic edema were investigated morphologically from the aspect of extracellular fluid (ECF)-cerebrospinal fluid (CSF) communication using horseradish peroxidase (HRP) injected into the cisterna magna as a marker. About 24 h after the induction of cold injury, HRP was distributed in the subjacent white matter of the lesion and around the ventricle. Forty-eight hours after injury, the distribution of HRP around the lesion became distinctive. This distribution of HRP became more concentrated at the same location on day 3-4 after injury. At this time, HRP was observed to be distributed along the walls of small vessels, in the cytoplasm of a few neurons and in the neuropil around the lesion by light microscopy. At small vessels around the lesion, a dense deposit of HRP at the basement membrane and many abluminal vesicles were evident by electron microscopy. These findings indicate that ECF-CSF communication changes drastically under the influence of edema fluid dynamics. In particular, the dense distribution of HRP around the lesion on day 3-4 after injury can be attributed to active retrograde transport by vessels in this area, a phenomenon considered important for edema resolution.

Postnatal development of neuropeptide Y-like immunoreactivity in area 17 of normal and visually deprived rhesus monkeys

Immunocytochemical methods were used to examine neuropeptide Y (NPY) immunoreactive neurons and fibers in area 17 of rhesus monkeys during the first year of life. NPY-immunoreactive (+) neurons are nonpyramidal cells which are either multipolar, bipolar, or bitufted in shape. They occur most frequently in layer 6 and the subjacent white matter, are sparser in the supragranular layers, and absent from layer 4C. Labeled somata in the supragranular layers are smaller compared to those in layer 6 and the white matter. A typical axon originates from the NPY+ soma or from a primary dendrite and frequently is varicose. Distribution and morphologies of NPY+ neurons in area 17 of infants are similar to those of adult monkeys. Thus, it seems that NPY+ neurons in rhesus monkeys are mature from birth. NPY+ fibers occur in area 17 from birth; however, they differ in density and distribution from those of older infant and adult monkeys. At birth, a prominent fiber plexus is found in the deepest part of layer 1, and another in the white matter. Immunoreactive processes are sparse in the remaining cortical gray, except for some vertical fibers extending from pia to white matter. By 4 months of age, labeled fibers form a coarse network in layers 2, 3, 5, and 6. In addition, a distinct plexus extends through layers 4B, 4A, and the lowest aspect of layer 3. Also, a thin immunoreactive fiber band is found at the bottom of layer 4C. In the remainder of layer 4C, NPY+ fibers are scant. The supragranular layers also exhibit a unique immunoreactive "snarl" of fibers. Increases in density of NPY+ processes in the older infants are gradual so that between 7 and 13 months of age, NPY+ fibers appear to have achieved adultlike densities. These observations indicate that NPY+ fibers in area 17 of newborn rhesus monkeys undergo postnatal maturation which reaches a plateau around 4 months of age. After monocular visual deprivation from birth to 4 months of age, either by eyelid suture or by occlusion with an opaque contact lens, density and distribution of NPY+ neurons and fibers, including snarls, appear similar to those of age-matched undeprived infants. Thus, disruption of the normal binocular input does not seem to arrest the maturation of the NPY system in area 17 of rhesus monkeys during a sensitive period of early postnatal development.

Cerebral Tuberous Sclerosis: Postmortem Magnetic Resonance Imaging and Pathologic Anatomy

We conducted postmortem magnetic resonance imaging (MRI) studies of five brains from patients with a clinical and pathologic diagnosis of tuberous sclerosis. Areas of prolonged T1 and T2 relaxation could easily be identified within the white matter subjacent to the cortical tubers despite formalin fixation and storage. The signal changes were identical to those reported in living patients with the disease. The detection of cortical tubers by MRI in two patients who were 34 and 35 years of age, respectively, at the time of death suggests that the signal changes on MRI are less affected by aging than are the low-attenuation changes on computed tomography, which are rarely identified in patients older than 27 years of age. Once the changes caused by fixation of tissues are considered, postmortem MRI is a viable investigative tool in studying tuberous sclerosis and other diseases, and it seems to correlate well with the MRI findings in living patients, as well as the gross and histopathologic changes seen at autopsy.