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A Wree

Publications and source records attributed to A Wree.

At least 19 recordsLinked to original sources

Nitric oxide synthase-containing neurons in the amygdaloid nuclear complex of the rat.

The nitric oxide-producing neurons in the rat amygdala (Am) were studied, using reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry. Almost all nuclei of the Am contained NADPHd-positive neurons and fibers, but the somatodendritic morphology and the intensity of staining of different subpopulations varied. The strongly stained neurons displayed labeling of the perikaryon and the dendritic tree with Golgi impregnation-like quality, whilst the dendrites of the lightly stained neurons were less successfully followed. Many strongly positive neurons were located in the external capsule and within the intraamygdaloid fiber bundles. A large number of small, strongly stained cells was present in the amygdalostriatal transition area. In the Am proper, a condensation of deeply stained cells occurred in the lateral amygdaloid nucleus. In the basolateral nucleus, the strongly NADPHd-positive neurons were few, and were located mainly along the lateral border of the nucleus. These cells clearly differed from the large, pyramidal, and efferent cells. The basomedial nucleus contained numerous positive cells but most of them were only lightly labeled. A moderate number of strongly stained neurons appeared in the medial division of the central nucleus, and a larger accumulation of strongly positive cells was present in the lateral and the capsular divisions. The medial amygdaloid nucleus contained numerous moderately stained neurons and displayed the strongest diffuse neuropil staining in Am. In the nucleus of the lateral olfactory tract, the first layer contained only NADPHd-stained axons, in the second layer, there were numerous moderately stained cells, and in the third layer, a few but deeply stained neurons. From the cortical nuclei, the most appreciable number of stained neurons was seen in the anterior cortical nucleus. The anterior amygdaloid area contained numerous NADPHd-positive neurons; in its dorsal part the majority of cells were only moderately stained, whereas in the ventral part the neurons were very strongly stained. The intercalated amygdaloid nucleus lacked NADPHd-positive neurons but an appreciable plexus of fine, tortuous axons was present. In the intra-amygdaloid part of the bed nucleus of the stria terminalis (st) some lightly stained cells were seen but along the entire course of st strongly stained neurons were observed. Some Am nuclei, and especially the central lateral nucleus and the intercalated nucleus, display considerable species differences when compared with the primate Am. The age-related changes of the nitrergic Am neurons, as well as their involvement in neurodegenerative diseases is discussed.

Amygdala↗

Brain stem afferent connections of the amygdala in the rat with special references to a projection from the parabigeminal nucleus: a fluorescent retrograde tracing study.

A recently revealed important function of the amygdala (Am) is that it acts as the brain's "lighthouse", which constantly monitors the environment for stimuli which signal a threat to the organism. The data from patients with extensive lesions of the striate cortex indicate that "unseen" fearful and fear-conditioned faces elicit increased Am responses. Thus, also extrageniculostriate pathways are involved. A multisynaptic pathway from the retina to the Am via the superior colliculus (SC) and the pulvinar was recently suggested. We here present data based on retrograde neuronal labeling following injection of the fluorescent tracer Fluoro-Gold in the rat Am that the parabigeminal nucleus (Pbg) emits a substantial, bilateral projection to the Am. This small cholinergic nucleus (Ch8 group) in the midbrain tegmentum is a subcortical relay visual center that is reciprocally connected with the SC. We suggest the existence of a second extrageniculostriate multisynaptic connection to Am: retina-SC-Pbg-Am, that might be very effective since all tracts listed above are bilateral. In addition, we present hodological details on other brainstem afferent connections of the Am, some of which are only recently described, and some others that still remain equivocal. Following selective injections of Fluoro-Gold in the Am, retrogradely labeled neurons were observed in parasubthalamic nucleus, peripeduncular nucleus, periaqueductal gray, dopaminergic nuclear complex (substantia nigra pars lateralis and pars compacta, paranigral, parabrachial pigmented and interfascicular nuclei, rostral and caudal linear nuclei, retrorubral area), deep mesencephalic nucleus, serotoninergic structures (dorsal, median and pontine raphe nuclei), laterodorsal and pedunculopontine tegmental nuclei (Ch6 and Ch5 groups), parabrachial nuclear complex, locus coeruleus, nucleus incertus, ventrolateral pontine tegmentum (A5 group), dorsomedial medulla (nucleus of the solitary tract, A2 group), ventrolateral medulla (A1/C1 group), and pars caudalis of the spinal trigeminal nucleus. A bilateral labeling of the upper cervical spinal cord was also observed.

Amygdala↗

Functional neuroanatomy of pain.

Pain is an unpleasant but important biological signal for danger. Nociception is necessary for survival and for maintaining the integrity of the organism in a potentially hostile environment. Pain is induced by noxious stimuli that act on a complex pain sensory apparatus. However, chronic pain no longer affords a protective role, but can become a ruining disease itself, termed "neuropathic pain". This contribution throws light on the complex machinery of pain processing, from the perspective of the connections between key structures that are necessary for a profound understanding of the phenomenon of pain.

Humans↗

Neurons in the dorsal column nuclei of the rat emit a moderate projection to the ipsilateral ventrobasal thalamus.

The dorsal column nuclei (DCN; gracile and cuneate nuclei) give rise to the medial lemniscus, the fibre system that provides an organised somatosensory input to the thalamus. Unlike the spinothalamic and trigeminothalamic tracts that project, also to the ipsilateral thalamus, the medial lemniscus system is believed to be entirely crossed. We demonstrate that DCN emit a small number of axons that reach the ipsilateral thalamus. As retrograde fluorescent neuronal tracer Fluoro-gold was stereotaxically injected in the ventrobasal thalamus of nine young adult Wistar rats. The injection foci were voluminous and encroached upon adjacent nuclei, but the periphery of the injection halo never spilled over to the contralateral thalamus. All sections of the contralateral gracile and cuneate nuclei and the midline nucleus of Bischoff contained abundant retrogradely labelled neurons. The comparison with the Nissl-stained parallel sections suggests that approximately 70-80% of the DCN neurons project to the contralateral thalamus. Counting of retrogradely labelled neurons in two cases revealed 4,809 and 4,222 neurons in the contralateral and 265 and 214 in the ipsilateral DCN, respectively. Thus, although less prominent than the ipsilateral spinothalamic tract, the lemniscal system also emits an ipsilateral projection that accounts for about 5% of the neuronal population in DCN that innervates the ventrobasal thalamus.

Afferent Pathways↗

Three-dimensional cytoarchitectonic analysis of the posterior bank of the human precentral sulcus.

Studies employing functional magnetic resonance imaging have identified the human frontal eye field as being in the anterior and partly in the posterior wall, as well as at the base of the precentral sulcus. Moreover, it is known that the frontal eye field extends rostrally to the superior frontal sulcus. According to Brodmann's cytoarchitectonic map, this region belongs to the dysgranular Brodmann area 6 of the premotor cortex. However, the frontal eye field in non-human primates has been located within the arcuate sulcus in Brodmann area 8, generating considerable debate about where to locate exactly the frontal eye field in humans. Functional studies of the primate frontal eye field have revealed a principal homology of voluntary saccadic control systems in human and old-world monkeys, especially the macaque. But these homologies seem to be contradicted by the reported topographic localization at the cytoarchitectonic level. Therefore, we studied the cytoarchitectonic structure of the posterior bank of the precentral sulcus of a human brain, employing newly developed spatial mapping techniques to provide data about whether or not this region should be considered cytoarchitecturally homogeneous or heterogeneous. We used functional magnetic resonance imaging results, as an initial guide in localizing a region which is activated by saccadic tasks. A maximum of activation was detected around the junction of the superior frontal sulcus and the precentral sulcus extending 1.5 cm along the precentral sulcus in direction of the lateral sulcus. Here, one human brain has been analyzed to obtain preliminary data about the cytoarchitectonical changes of a part of area 6. Statistical analysis of the three-dimensional architectonic data from this region allowed us to identify a zone at the posterior bank, which in other studies has been associated with a functional region that controls pursuit eye movements and performs sensory-to-motor transformations. We found two significant sectors along the ventral part of the posterior bank of the precentral sulcus. The caudal transition region coincides partly with a region that integrates retinal and eye position signals for target location, arm, and axial movements. The second more ventrally located region is attributed to process oral-facial movements. The caudal transition region coincides with our functional magnetic resonance imaging investigation. It was revealed that this region lies at the inferior frontal eye field, where a pronounced activation over a larger region can be stimulated. Currently, more studies are needed to combine functional magnetic resonance imaging data of maximal activation with data from whole histologic brain sections of more individuals and to quantify the variability of this region and its sub-regions by means of a standardized brain atlas.

Aged↗

Distribution of [3H]MK-801, [3H]AMPA and [3H]Kainate binding sites in rat hippocampal long-term slice cultures isolated from external afferents.

The distribution of ionotropic glutamate receptors in transverse hippocampal sections and along the septotemporal hippocampal axis can be correlated to hippocampal connectivity, in particular to area- and layer-specific termination zones of afferents. However, in isolated organotypic hippocampal slice cultures developing without extrinsic afferent input no systematic studies exist about the distribution of glutamate receptors. In the present study we used receptor autoradiography to examine [3H]MK-801, [3H]AMPA and [3H]Kainate binding sites in hippocampal slice cultures prepared from 6-day-old rats. After 24 days in vitro layer-specific concentrations of [3H]MK-801, [3H]AMPA and [3H]Kainate binding sites were compared to age-matched hippocampi in situ (P30 rats). An obvious difference between hippocampal slice cultures and hippocampi in situ was a changed distribution of binding sites among the hippocampal areas showing a relative increase of [3H]MK-801 and [3H]AMPA binding sites in CA3 as compared to CA1 and to the dentate gyrus in the cultures. In CA1, however, the relative layer-specific distributions of [3H]MK-801 and [3H]AMPA binding sites were identical in hippocampal slice cultures and in hippocampi in situ. Interestingly, layer-specific binding of [3H]Kainate in the cultures exceeded that in the hippocampi in situ 3-5 times. Moreover, in the cultures the binding of the three ligands varied systematically showing gradients along the "superficiomembranal" axis. Cultures taken from different positions along the hippocampal axis differed with respect to concentrations of [3H]MK-801 and [3H]Kainate binding sites, but not of [3H]AMPA binding sites. The results suggest a massive sprouting and reorganisation of intrinsic projections in long-term hippocampal slice cultures.

Afferent Pathways↗

Immunocytochemical characterization of in vitro PKH26-labelled and intracerebrally transplanted neonatal cells.

The lipophilic dye PKH26 that binds irreversibly to cell membranes has been used to label various cell types in vitro prior to transplantation in order to recognize grafted cells posttransplantationally in the host tissue by fluorescence microscopy. The purpose of the present study was to optimize immunocytochemical staining procedures for PKH26-containing specimens in cell culture and after transplantation into rat brain. We demonstrated that freeze-thawing allowed for proper immunostaining of intracellular epitopes whereas PKH26-labelling was preserved. PKH26-labelled donor cells were detectable at least up to 4 months after transplantation in the host brain.

Animals↗

Septotemporal distribution of [3H]MK-801, [3H]AMPA and [3H]Kainate binding sites in the rat hippocampus.

The distribution of glutamate receptors in transverse hippocampal sections has been well investigated. However, in spite of the known septotemporal gradients of hippocampal connectivity no systematic studies exist about the distribution of glutamate receptors along the septotemporal (longitudinal) hippocampal axis. Therefore, in the present study this issue was investigated using receptor autoradiography for the [3H]MK-801, [3H]AMPA and [3H]Kainate binding sites. Hippocampi from 30-day-old rats were sectioned perpendicularly to their longitudinal axis, yielding a total of 25-30 equidistantly spaced autoradiographs for each hippocampus. For each section layer-specific concentrations of binding sites were calculated by the aid of a computerized image analysing system. The dependency of concentrations of binding sites on the septotemporal position was evaluated by regression analysis. Gradients of binding were confined to distinct hippocampal layers. Significant septotemporal gradients of [3H]MK-801 binding were observed in selected layers of CA1 and the dentate gyrus, a septal to temporal decrease of binding in the oriens and radiatum layers of CA1 being most prominent. For [3H]AMPA, significant septotemporal gradients of binding were restricted to layers of CA3, CA4 and the dentate gyrus, with values generally increasing from septal to temporal levels. The observed septotemporal gradients possibly reflect functional segregations along the longitudinal hippocampal axis and could be important for the comparability of ligand binding studies using transverse hippocampal sections or hippocampal slice cultures.

Animals↗

In situ hybridization for somatostatin mRNA in the adult rat: cingulate, insular, prepiriform, perirhinal, entorhinal, and retrosplenial cortical regions.

The expression of somatostatin mRNA within the allocortex of the rat was examined by in situ hybridization with an alkaline phosphatase labeled probe. We sought to determine whether parcellation of the allocortex could be based upon the number and laminar location of the hybridized cells and to contrast the allocortical features with those of the isocortical areas. The cingulate region was characterized by intense, moderate, and faint cells, small to medium in size throughout the laminae. The retrosplenial region demonstrated a somewhat stratified appearance with an abundance of cells expressing somatostatin mRNA in the upper portion of the composite layer II-IV and also in the upper portion of layer VI. The insular region displayed more heterogeneity. The distribution of the cells hybridized for somatostatin mRNA formed distinctive configurations within the insular region (dorsal and ventral agranular insular areas) with no obvious generality. The perirhinal area resembled the ventral agranular insular area, and the cell distribution of the entorhinal and prepiriform areas displayed a common characteristic in that the primary axis of the perikarya of somatostatin mRNA expressing cells within the lower layers were oriented at almost every possible angle. The conclusion of the investigation is that in situ hybridization for somatostatin mRNA provides a means by which the areal boundaries within the allocortex may be drawn.

Animals↗

Functional cerebral activity during regeneration from entorhinal lesions in the rat.

The consequences of an unilateral electrolytic entorhinal lesion on the functional activity in all major anatomically defined brain regions were evaluated in the rat. The 14C-2 deoxyglucose method served as a tool to quantify alterations of local cerebral glucose utilization (LCGU) ipsilateral and contralateral to the lesion at 4 days, 2 weeks, or 3 months after stereotaxic surgery. Apart from a few minor increases in the contralateral hemisphere, the predominant pattern consisted of reductions in the range of 10-40% in the ipsilateral hemisphere. Ipsilaterally, in extrahippocampal areas, LCGU had regained control levels at 2 weeks postlesion in contrast to hippocampal regions, where reductions were more pronounced than in other brain areas and partially persisted for up to 3 months. Interestingly, the termination zones of entorhinal fibers in the dentate gyrus did not regain control levels within 3 months. We conclude from the data that functional recovery of denervated primary target areas does not occur within 3 months after entorhinal lesions and that altered functional activity may be found beyond the primary target areas predominantly during the acute recovery period after the lesion. The data suggest that sprouting fibers do not reestablish a fully functional neuronal network during the recovery period.

Animals↗

Local cerebral glucose utilization in perfusion-fixed rat brains.

Local cerebral glucose utilization (LCGU) was measured in 75 cortical areas and nuclei of adult, 3-4-month-old Wistar rats, using the [14C]2-deoxyglucose (2-DG) technique. Measurement of total brain radioactivity content was not significantly different in unfixed material compared to fixed brain tissue. Values of LCGU derived from fresh, unfixed material were compared with values obtained from rats fixed by perfusion 45 min after the [14C]2-DG bolus injection with phosphate-buffered 3.3% paraformaldehyde at room temperature. In the fixed material, the mean LCGU of all brain regions was significantly increased by about 25% compared with the unfixed specimen due to tissue shrinkage of 7.2% in the fixed brains. Shrinkage leading to a higher volume density of [14C]2-deoxyglucose-6-phosphate in brain tissue results in a higher grain density in the respective autoradiographs. The wash-out of blood-borne [14C]2-DG is negligible except for blood-rich structures like the pineal gland and the choroid plexus.

Animals↗

Transplants of embryonic cortical tissue placed in the previously damaged frontal cortex of adult rats: local cerebral glucose utilization following execution of forelimb movements.

Transplantation of fetal cortical tissue into the motor cortex of adult rats was used as an experimental model to examine the functional integration of homotopic fetal neocortical grafts into the motor pathways of adult host brain. We have employed the [14C]2-deoxy-D-glucose method to analyse the metabolic activity of the transplant and host sensorimotor cortex: (i) in animals solicited to perform specific lever-pressing movements with the limb contralateral to the transplant (experimental group); and (ii) in non-solicited animals or in animals using the limb ipsilateral to the transplant (control group). Grafts in the control group displayed homogeneous uptake of 2-deoxy-D-glucose throughout the rostrocaudal extent of the transplant. The local cerebral glucose utilization levels were low as compared to those of the surrounding cortex but were at least two-times higher than in the corpus callosum. Increase in 2-deoxy-D-glucose uptake by the transplant cells was found only in the experimental group. In this group, 2-deoxy-D-glucose uptake was higher in the caudal (AP: +3.0 to +1.7 mm, relative to Bregma) than in the rostral sectors of the transplants suggesting the existence of a topographic organization within the transplant. In addition, except in the rostral part, glucose utilization was higher in the transplant of the experimental group than in the sensorimotor areas of the non-activated cortex in the control group. Moreover, glucose utilization of the transplant cells was systematically higher in the experimental than in the control group. The transplants appear to display a certain level of metabolic integration with the host sensorimotor cortex since, in the experimental group, there was no significant differences in local cerebral glucose utilization values in the caudal sector of the transplant and in the surrounding sensorimotor cortical areas of the host. The 2-deoxy-D-glucose uptake was even higher in the caudal sector of the transplant than in some of the subfields of the contralateral sensorimotor cortex. The present findings indicate for the first time that motor activation of the contralateral forelimb produces an increase in metabolic activity in distinct transplant sectors, the topographic distribution of which matches the normal topographic organization of the forelimb somatomotor map. This suggests that transplants of embryonic frontal neocortex placed in the frontal cortex of adult hosts become functionally integrated with the host motor system.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Occurrence of a musculus abductor digiti minimi longus.

Whilst dissecting the body of a 79 year old male we observed an accessory muscle in the right lower limb which has not yet been described. The Musculus abductor digiti minimi longus consisted of two portions originating from the dorsal parts of the supracondylar regions of the fibula and the tibia. Both heads merged distally forming a 2 mm thick tendon that curved around the Malleolus medialis, ran across the deep Planta pedis and inserted together with the Musculus abductor digiti minimi at the Facies lateralis of the Phalanx proximalis digiti quinti.

Aged↗

Chronic depression of glucose metabolism in postischemic rat brains.

BACKGROUND AND PURPOSE: The present investigation aimed to quantify functional activity in rat brains after long-term recovery from transient forebrain ischemia. METHODS: With the use of the [14C]2-deoxyglucose method, local cerebral glucose utilization was measured in 62 cortical and subcortical brain regions in postischemic rat brains. Transient forebrain ischemia of 10 minutes' duration was induced by clamping the common carotid arteries and simultaneously lowering blood pressure to 40 mm Hg. Rats survived the insults for 1 week, 2 weeks, 3 weeks, or 3 months. RESULTS: Reductions predominated in the majority of gray matter structures at all time points investigated (P < .05). Except for a few areas, recoveries of local cerebral glucose utilization to preischemic levels did not occur. CONCLUSIONS: The data illustrate that widespread alterations of functional activity prevail in postischemic brains beyond the selectively vulnerable regions. The present functional data are in line with previous stereological results of reduced fresh volumes in the majority of postischemic brain structures. The data suggest that chronic alterations of ischemic brains are not confined to the selectively vulnerable regions.

Animals↗

Parcellation of cortical areas by in situ hybridization for somatostatin mRNA in the adult rat: frontal, parietal, occipital, and temporal regions.

The expression of somatostatin mRNA within the neocortex of the rat was examined by in situ hybridization with an alkaline phosphatase-labeled probe. We sought to determine whether parcellation of the neocortex could be based upon the number and laminar location of the hybridized cells. Our investigation demonstrated that the boundaries of the neocortical areas can be determined by the distribution pattern of neurons expressing somatostatin mRNA. Few hybridized cells were located within layer IV, and this sparsity of cells within their wide granular layer marked the primary sensory areas. The occipital region was stratified, with intensely labeled cells in layers II/III and VI and faintly labeled cells in layer V. The parietal region carried a similar stratification, but more space between intensely labeled cells in layers III and V and between layers V and VI gave the region a three-tiered appearance. The temporal region displayed intensely labeled cells dispersed throughout layers III and VI and many in layer V as well as those faintly labeled without any breaks between the laminae. The distribution of the cells hybridized for somatostatin mRNA formed two configurations within the frontal region. It was difficult to identify any lamination in the first area, whereas the second area demonstrated a stratification reminiscent of the parietal region, but with only two tiers. The conclusion of the investigation is that in situ hybridization fro somatostatin mRNA provides an exceptional means by which the area boundaries within the neocortex may be drawn.

Animals↗

Brain-derived neurotrophic factor protects against ischemic cell damage in rat hippocampus.

The neuroprotective action of brain-derived neurotrophic factor (BDNF) was evaluated in a rat model of transient forebrain ischemia. A continuous intraventricular infusion of BDNF for 7 days starting immediately before the onset of ischemia significantly increased the number of pyramidal cells in the vulnerable CA1 sector of the hippocampus. In situ hybridization experiments suggest the neuroprotection to be mediated via trkB-receptors in the hippocampus. The data indicate a therapeutic potential for the treatment of cerebral ischemia.

Animals↗

Metabolic mapping of the forelimb motor system in the rat: local cerebral glucose utilization following execution of forelimb movements mainly involving proximal musculature.

The present study was undertaken to establish a metabolic map of forelimb motor pathways under conditions of physiological activation. For that purpose, we used the [14C]2-deoxy-D-glucose (2-DG) method to identify forebrain and midbrain centers showing an increase in 2-DG uptake in animals trained to execute specific lever-pressing movements with the right forelimb. Following repetitive execution of these movements, principally involving proximal (shoulder, elbow, and wrist) muscles, increases in 2-DG uptake were found contralaterally in several neocortical or subcortical centers. The largest left-right differences in local cerebral glucose utilization (LCGU) were found in a central region of the sensorimotor cortex composed of the caudal part of area 3 of the frontal cortex (Fr3; p < 0.01), the intermediate part of area 1 of Fr (Fr1; p < 0.01), and the forelimb cortical area (p < 0.04). Fr3 was the brain center with the highest differences in left-right LCGU. This central region of the sensorimotor cortex seems to correspond closely to the caudal forelimb area of Neafsey et al. (1986). Intermediate left-right differences in LCGU were found (1) in the just-adjoining rostral-medial areas of the motor cortex involving the intermediate part of area 2 of Fr (Fr2; p < 0.01) and the rostral part of Fr1 (p < 0.04), and (2) in the rostral part of area 1 of the parietal cortex (Par1; p < 0.01) and the caudal part of area 2 of Par (Par2; p < 0.05), both corresponding to forelimb representation. Weak (not statistically significant) left-right differences in LCGU were found in the rostral parts of Fr2 and Fr3, in the caudal parts of Fr2 and Fr1, in the hindlimb cortical area, and in the caudal part of Par1 and the rostral part of Par2. In the remaining cortical areas (cingulate; agranular and granular retrosplenial; temporal; and occipital), there was practically no difference in left-right 2-DG uptake. In addition, increased 2-DG uptake was present contralaterally in several subcortical motor-related centers. In those centers in which a somatomotor map has been established (caudate putamen, ventral lateral and ventral posterolateral thalamic nuclei, and red nucleus), increased 2-DG uptake was found in regions corresponding to forelimb representation.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗

Assessing chronic brain damage by quantification of regional volumes in postischemic rat brains.

The present study provides data on fresh volumes of 39 anatomically defined brain regions after a 10 min transient forebrain ischemia in the rat. Ischemia was induced by occlusion of the carotid arteries and simultaneous hypotension. After a survival period of 3 months the rats were transcardially perfusion-fixed with Bodian's solution, and the brains processed for paraffin embedding and serially sectioned. The sections were Nissl-stained for delineation of the brain regions. The volume of a brain region was calculated from 8-10 equidistant sections, using the Cavalieri method and corrected for shrinkage of the brain. Fresh volumes were reduced by 27-50% in the layers of the hippocampal CA1 sector, by 40-46% in the substantia nigra, by 19% in the caudate nucleus, by 13% in the subiculum and the cingulate areas 1-3, by 12-14% in the retrosplenial and temporal areas. The results show that determination of fresh volumes is a sensitive method for quantification and localization of ischemic brain damage in the whole brain.

Animals↗