Pontine Gray Matter Research Articles

Pattern of tau hyperphosphorylation and neurotransmitter markers in the brainstem of senescent tau filament forming transgenic mice

The early occurrence of brainstem-related symptoms, e.g. gait and balance impairment, apathy and depression in Alzheimer's disease patients suggests brainstem involvement in the initial pathogenesis. To address the question whether tau filament forming mice expressing mutated human tau mirror histopathological changes observed in Alzheimer brainstem, the degree and distribution of neurofibrillary lesions as well as the pattern of cholinergic and monoaminergic neurons were investigated. The expression of the human tau transgene was observed in multiple brainstem nuclei, particularly in the magnocellular reticular formation, vestibular nuclei, cranial nerve motor nuclei, sensory trigeminal nerve nuclei, inferior and superior colliculi, periaqueductal and pontine gray matter, and the red nucleus. Most of the human tau-immunoreactive cell groups also showed tau hyperphosphorylation at the epitopes Thr231/Ser235 and Ser202/Thr205, while abnormal tau phosphorylation at the epitope Ser422 or silver stained structures were almost totally lacking. We found no obvious differences in distribution and density of cholinergic and monoaminergic neurons between tau-transgenic and wild type mice. Although numerous brainstem nuclei in our model expressed human tau protein, the development of neurofibrillary tangles, neuropil threads and ghost tangles was rare and likewise its distribution differed largely from Alzheimer's disease pattern. The number of monoaminergic neurons remained unchanged in the transgenic mice, while monoaminergic nuclei in Alzheimer brainstem showed a distinct neuronal loss. However, the distribution of pretangle-affected neurons in the tau-transgenic mice partly resembled those seen in progressive supranuclear palsy, presenting these animals as a model to examine brainstem pathogenesis of progressive supranuclear palsy.

Distribution of L1cam mRNA in the adult mouse brain: In situ hybridization and Northern blot analyses

Previous immunohistochemical analysis revealed a wide distribution of L1cam-positive neural and nonneural structures in adult mouse brain. Although there were numerous punctate immunoreactive nerve terminals, only a few immunoreactive neuronal cell somata were present (Munakata et al. [2003] BMC Neurosci. 4:7). To explore the distribution of L1cam mRNA-containing cells, which are interpreted to be L1cam-producing cells, we performed in situ hybridization histochemistry with an antisense L1cam cRNA probe. L1cam mRNA was distributed widely from the olfactory bulb to the upper cervical cord with an uneven localization pattern in adult brain. All positive cell somata with silver grains after emulsion autoradiography were neuronal, and no grains were detected on nonneural cells in the present study. A high density of signals for neuronal L1cam mRNA was found in the thalamus, mammillary body, and hippocampus. In addition, strong hybridization signals were localized in various nuclei: main and accessory olfactory bulb, compact part of the substantia nigra, pontine gray matter, tegmental reticular nucleus, Edinger-Westphal nucleus, trigeminal motor nucleus, locus coeruleus, mesencephalic trigeminal nucleus, raphe nuclei, facial nucleus, ambiguus nucleus, dorsal motor vagal nucleus, and inferior olivary nucleus. Some long projection neurons such as the pyramidal, mitral, principal neurons of several cranial nuclei, and presumably monoaminergic cells containing noradrenalin, dopamine, and serotonin, expressed high levels of L1cam.

Study on the etiopathogenesis of multiple spongy necrosis of the pontine base in three autopsy cases.

The etiopathogenesis of multiple spongy necrosis (MSN) of the pontine base was analyzed by examining the spatial relationship with intra- and extrafascicular vascular structures by reconstruction of serial sections of nine lesions from three autopsy cases. All nine lesions in the fascicles were distributed without any spatial relationship to the intrafascicular vessels. Instead, these lesions were distributed in parallel with arterial and venous transverse main branches between the anteromedial and anterolateral groups of the pontine vessels. On the other hand, all lesions in the middle cerebellar peduncle were arranged obliquely along the arterial and venous main trunks of the lateral group vessels with sparing of the perivascular narrow zone of the white matter. Moreover, narrow fascicles, even though located in the dorsomedial region of the pontine base, which is consistently involved in MSN, were spared, and thick transverse and longitudinal fascicles were selectively involved. The marginal zone of fascicles was spared, and focal coagulation necrosis was sometimes found in MSN lesions. Additionally, normal fascicles did not have their own nutritional arteries, and were nourished by arterioles and capillaries from the surrounding pontine gray matter. Neither severe organic stenosis nor occlusion of pontine vessels was found. On the basis of the close topographical relationship of MSN lesions with the pontine vascular architecture in addition to preferential involvement of thick fascicles with sparing of the marginal zone and inclusion of focal coagulation necrosis, it is proposed that the etiopathogenesis of MSN is pontine ischemia on a background of the characteristic parenchymal and vascular architecture of the pontine base. As to the cause of the ischemia, it is proposed that some functional disorder such as arterial vasoconstriction in the pontine base or the vertebrobasilar artery is responsible, rather than organic changes in the vessels.

Morphology of visual cortical neurons projecting to the pons. A study with intracellular injection of lucifer yellow in the cat.

The aim of this study is to describe the morphological features of the origin cells of the visual corticopontine projection in the cat. To this end, the pontine grey matter of adult cats was injected with Rhodamine Latex Microspheres. The resulting, retrogradely marked cells of the visual cortex, were subsequently injected intracellularly with Lucifer Yellow. The majority of these cells (68%) were layer V pyramidal cells. However, a significant proportion of these retrogradely-labeled cells were atypical (26.5%) and non-pyramidal (5.5%) in their morphology. The majority of the labeled cells were found at the interhemispheric surface. The somatic dimensions of the visual corticopontine cells were on average 22.8 x 17.0 microns. The mean number of basal dendrites of pyramidal cells was 5.3 and their average tangential spread was 296.1 microns. For non-pyramidal cells, the values were 3.2 and 195.6 microns respectively. The main bifurcation of apical dendrites was located on average at 95.0 microns from the soma and their mean tangential spread was 193.9 microns. The depth of the soma was on average 1086.9 microns from the pial surface.

Course and Collaterals of Corticospinal Fibers Arising from the Sensorimotor Cortex of the Reeler Mouse

The reeler genetic mutation, occurring spontaneously in mice, affects migration of neuroblasts in the central nervous system at its last stage, causing severe cytoarchitectonic abnormalities in laminated structures, such as the cerebral and cerebellar cortex. In the reeler mouse, corticospinal (CS) neurons are malpositioned in association with the deranged laminar cytoarchitecture. To examine whether CS projections in the reeler mouse and their collaterals terminating with subcortical nuclei are normal or not, 5% biocytin was injected into the sensorimotor cortex of 2-month-old normal and reeler mice. Anterogradely labeled CS fibers of normal and reeler mice exited from the cortex and entered the internal capsule and the cerebral peduncle. They penetrated the basal pontine gray matter as longitudinal pontine fibers and entered the medullary pyramid. They continued caudally as a compact bundle along the ventral surface of the medulla, passed through the pyramidal decussation at the spinomedullary junction and entered the contralateral dorsal funiculus of the spinal cord. Both in normal and reeler mice, collaterals arising from these CS fibers projected to the ipsilateral red nucleus, basal pontine gray matter, inferior olivary complex, and the contralateral gracile nucleus. Thus, in the reeler mouse, the course and termination of CS fibers and their collaterals are identical to their normal counterparts, suggesting that radially malpositioned CS neurons in the sensorimotor cortex project to the subcortical nuclei in a manner similar to normal CS neurons.

Regional differences in inhibition and recovery of protein synthesis after transient hindbrain ischaemia of gerbils.

Regional protein synthesis was estimated autoradiographically in a model of transient hindbrain ischaemia of gerbils. In studies of 5 min ischaemia followed by 5 min recirculation, incorporation of [14C]valine into the TCA-insoluble protein fraction was not affected. In studies of 15 min ischaemia followed by 5 min recirculation, incorporation of the tracer into the protein fraction was severely depressed in the ischaemic lesion of the brain stem and cerebellum. However, the granular layer of the cerebellar cortex had partially preserved protein synthesis. When recirculation time was extended to 2 h after 30 min ischaemia, protein synthesis of the cerebellar cortex almost recovered to the full level of the control. However, in the pontine grey matter, inferior colliculus and vestibular nucleus, a significant reduction in protein synthesis persisted. These results indicate that protein synthesis in the pontine grey matter, inferior colliculus and vestibular nucleus are selectively inhibited by ischaemia. Further its recovery after recirculation is slow. The cerebellar cortex is less vulnerable to ischaemia, and recovery is relatively fast. The regional heterogeneity of protein synthesis is neither due to the degree of ischaemia in this model nor the extent of postischaemic hypoperfusion. Factors that influence protein synthesis in this ischaemic model are discussed.

A TRH analog (DN-1417): effects on local cerebral glucose utilization in conscious and pentobarbitalized rats determined by the autoradiographic 2-deoxy-[14C]glucose method.

Effects of a TRH (thyrotropin-releasing hormone) analog, DN-1417 (gamma-butyrolactone-gamma-carbonyl-L-histidyl-L-prolinamide citrate), with regard to the rate of local cerebral glucose utilization (LCGU) were assessed using the autoradiographic 2-deoxy-D-[14C]glucose method to clarify the possible sites of action in conscious and pentobarbitalized rats. DN-1417 (0.5-5 mg/kg, i.v.) significantly shortened the pentobarbital-induced sleeping time in a dose dependent manner, and this effect of DN-1417 was reduced by intracerebroventricular (i.c.v.) pretreatment with atropine methylbromide (20 micrograms). DN-1417 (5 mg/kg, i.v.) by itself slightly increased the LCGU in the thalamus dorsomedial nucleus and mammillary body and significantly increased it in the septal nucleus. Pentobarbital (30 mg/kg, i.v.) alone produced a marked and diffuse reduction in LCGU throughout the brain at a rate of about 46% of the control. DN-1417 (5 mg/kg, i.v.) markedly reversed the reduction of LCGU induced by pentobarbital. The antagonistic effect of DN-1417 in LCGU was about twice as potent as that of TRH. Locally, significant reversal effects by DN-1417 were observed in the hypothalamus, septal nucleus, hippocampus, mammillary body, thalamus dorsomedial nucleus, caudate-putamen, nucleus accumbens, pontine gray matter and so on. These actions of DN-1417 were almost completely abolished in all areas except for the visual cortex under the condition of pretreatment with atropine methylbromide (20 micrograms, i.c.v.). On the other hand, pimozide (1 mg/kg, i.p.) augmented the actions of DN-1417. Thus, DN-1417 seems to act on the level of consciousness via a reticulo-thalamo-cortical system, and reverses the LCGU reduction induced by pentobarbital via a cholinergic mechanism. The hypothalamus appears to be a crucial site in mediation of the antagonistic action of DN-1417 on pentobarbital.

A TRH ANALOG (DN-1417): EFFECTS ON LOCAL CEREBRAL GLUCOSE UTILIZATION IN CONSCIOUS AND PENTOBARBITALIZED RATS DETERMINED BY THE AUTORADIOGRAPHIC 2-DEOXY-[14C]GLUCOSE METHOD

Effects of a TRH (thyrotropin-releasing hormone) analog, DN-1417 (r-butyrolactone-r-carbonyl-L-histidyl-L-prolinamide citrate), with regard to the rate of local cerebral glucose utilization (LCGU) were assessed using the autoradiographic 2-deoxy-D-[14C]glucose method to clarify the possible sites of action in conscious and pentobarbitalized rats. DN-1417 (0.5-5 mg/kg, i.v.) significantly shortened the pen-tobarbital-induced sleeping time in a dose dependent manner, and this effect of DN-1417 was reduced by intracerebroventricular (i.e.v.) pretreatment with atropine methylbromide (20 βg). DN-1417 (5 mg/kg, i.v.) by itself slightly increased the LCGU in the thalamus dorsomedial nucleus and mammillary body and significantly increased it in the septal nucleus. Pentobarbital (30 mg/kg, i.v.) alone produced a marked and diffuse reduction in LCGU throughout the brain at a rate of about 46% of the control. DN-141 7 (5 mg/kg,i.v.) markedly reversed the reduction of LCGU induced by pentobarbital. The antagonistic effect of DN-1417 in LCGU was about twice as potent as that of TRH. Locally, significant reversal effects by DN-1417 were observed in the hypothalamus, septal nucleus,hippocampus, mammillary body, thalamus dorsomedial nucleus, caudate-putamen,nucleus accumbens, pontine gray matter and so on. These actions of DN-1417 were almost completely abolished in all areas except for the visual cortex under the conditionof pretreatment with atropine methylbromide (20 μ, i.c.v.). On the other hand, pimozide (1 mg/kg, i.p.) augmented the actions of DN-1417. Thus, DN-1417 seems to act on thelevel of consciousness via a reticulo-thalamo-cortical system, and reverses the LCGU reduction induced by pentobarbital via a cholinergic mechanism. The hypothalamus appears to be a crucial site in mediation of the antagonistic action of DN-1417 on pentobarbital.

Immunocytochemical study of Myelin-associated Glycoprotein (MAG) and Basic Protein (BP) in acute Experimental Allergic Encephalomyelitis (EAE)

To compare distributions of oligodendroglial myelin-associated glycoprotein (MAG) and myelin basic protein (BP) during demyelination in acute experimental allergic encephalomyelitis (EAE). Lewis rats were sensitized with an emulsion containing guinea pig spinal cord and complete Freund's adjuvant. The rats were examined clinically and groups were perfused with fixative before symptoms appeared (7d), within 48 h of symptom onset (10d) and during more severe illness (14d, 21d). Paraffin sections of cerebrum, brainstem, and spinal cord were immunostained with antisera to MAG and BP. Other sections in each serially mounted series were stained with luxol fast blue, hematoxylin and eosin or with the Bodian method to correlate MAG and BP results with histological changes. No abnormalities were detected 7d after sensitization. After 10d, small perivenular inflammatory cell infiltrates were present in white matter, displaced myelinated fibers, but their MAG stained periaxonal regions and BP-stained myelin sheaths appeared normal. In pontine grey matter lesions, there were focal abnormalities in a few myelin sheaths. After 21d, demyelinating lesions were present that were largest in pontine grey matter. Decreased MAG staining was present in areas of myelin sheath loss. MAG-stained fragments were found in zones of active myelin breakdown but no decrease or other change in MAG staining extended beyond the margins of demyelinating lesions into areas with normally stained myelin sheaths. Thus, in contrast to multiple sclerosis (Itoyama et al. 1980), changes in periaxonal oligodendroglial MAG are not present in acute EAE before inflammatory cell infiltrates or myelin sheath changes appear. Our findings suggest that myelin sheaths are the primary targets in EAE-induced demyelination. Oligodendroglia appear to be relatively unaffected and are available to remyelinate axons.

The significance of local cerebral glucose utilization determined by the autoradiographic [14 C] deoxyglucose method in experimentally induced coma.

Bilateral lesions made in the midbrain reticular formation of the rat produced behavioral akinesia. These animals neither ate nor drank. EEGs of these animals usually showed high voltage slow waves at rest. Slight EEG arousal response was demonstrated by clapping, touching and pinching only in rats with moderate impairment. Concerning the rates of local cerebral glucose utilization (LCGU) measured by means of the autoradiographic [14C] deoxyglucose method, 13 structures exhibited significant reductions in 28 gray structures examined when compared with sham operated rats. Lesions in the midbrain reticular formation resulted in reduction of LCGU in the neocortex, ventral nucleus of the thalamus, subthalamic nucleus, and medial and lateral geniculated bodies, mamillary body, septal nucleus and caudateputamen. Structures which did not show any significant change in LCGU were those related to the paleo and archi-cortices. These findings suggest the existence of two types of ascending activating systems. Administration of 30 mg/kg of pentobarbital reduced LCGU diffusely throughout the brain. When thyrotropin releasing hormone (TRH) was administered to rats with lesions in the midbrain reticular formation, reversal of the reduction of LCGU was observed in the dorsomedial nucleus of the thalamus and the mamillary body. Reversal of LCGU in the dorsomedial nucleus of thalamus was especially significant and its level exceeded the level of the sham control value. This suggests TRH might exert its function through the dorsomedial nucleus of the thalamus and mamillary body. When TRH was administered to rats treated with pentobarbital, significant reversal was observed in the following structures: the lateral and ventral nucleus of the thalamus, dentate gyrus, caudate-putamen, nucleus accumbens, pontine gray matter, and raphe nucleus.

Corticopontine projections from the cingulate cortex in the rhesus monkey

The corticopontine projections of the cingulate cortices were investigated in the rhesus monkey with the use of autoradiography. A well-organized topography of projections was observed with anterior cingulate cortex projecting to the medial part of the pontine gray matter and posterior cingulate cortex projecting to the lateral part. Together these projections form a circle of termination around the periphery of the pontine gray matter.

Pontosubicular Necrosis and Hyperoxemia

Pontosubicular necrosis (PSN) is confined to a short perinatal developmental period and is apparently related to asphyxia at birth. Neuronal necrosis with karyorrhexis and proliferative changes in astrocytes are most prominent in the pontine gray matter and subiculum of the hippocampus. We have observed a striking association of PSN in neonates with high arterial blood oxygen (PO2) levels during the first week of life. All autopsies performed on neonates in 1977 at Magee-Womens Hospital (University Health Center of Pittsburgh) were reviewed, and all 64 neonates who survived long enough to have multiple PO2 determinations were studied. All had severe hypoxia, respiratory distress, and/or apnea. Twenty-seven (group I) did not have PO2 levels higher than 150 torr whereas 37 (group II) had PO2 levels higher than 150 torr for a sustained period. PSN was not seen in group I; it was prominent in group II. PSN was most severe between the gestational ages of 26 to 36 weeks. Hyperoxemia may decrease cerebral blood flow selectively at this critical phase of development or there may be a greater sensitivity to the toxic action of high blood oxygen levels in the presence of acidosis and hypoxia. A combination of these factors seems most probable.

A post-vaccinal inclusion body encephalitis in dogs.

Two separate episodes of an encephalitis occurred in dogs after the administration of a few batches of a combined, live attenuated distemper/hepatitis virus vaccine. The lesions consisted of eosinophilic intranuclear and intracytoplasmic inclusions in large neurones, together with a nonsuppurative encephalitis and malacia of the ventral pontine gray matter. The presence of nucleocapsid, indistinguishable from that seen in distemper infection, indicates that a distemper or distemper-like virus was directly involved.