Development of parvalbumin-immunoreactive neurons in the postnatal human hippocampal formation.

Introduction: Parvalbumin (PV) is a calcium-binding protein present in fast-spiking GABAergic neurons, such as basket and axo-axonic cells. Previous studies in non-human primates reported prenatal expression of PV in the temporal archicortex including entorhinal cortex and hippocampal formation. In contrast, PV-immunoreactivity was observed only postnatally in the human entorhinal cortex. Regarding PV expression in the human hippocampal formation, no information is available. Methods: In this study, the neurochemical maturation of PV-immunoreactive interneurons was studied in the postnatal developing human hippocampal formation. Results: Before birth, no PV-immunoreactive neurons could be detected in the human hippocampus. At birth, only a few PV-immunoreactive neurons were visible in Ammon's horn. The first PV-immunoreactive cells in the hilus of the dentate gyrus appeared at the age of 1 month. Even at the age of 5 months, only a few PV-immunopositive cells were present in the dentate hilus. The number of cells and their dendritic and axonal arborization in Ammon's horn and in the dentate gyrus gradually increased with age. Even at the age of 2 years, dendritic tree and axons of PV-immunoreactive neurons were less complex than can be seen in 8 and 11 years old children. Discussion: Our results showed that long-lasting maturation of PV-immunoreactive interneurons follows the developmental sequence of the subfields of the human hippocampal formation and provides further morphological evidence for the long-lasting functional maturation of the human cortex.

Effect of Air-Polishing and Different Post-Polishing Methods on Surface Roughness of Nanofill and Microhybrid Resin Composites.

Air-abrasion is a popular prophylactic procedure to maintain oral hygiene. However, depending on the applied air-abrasive powder, it can damage the surface of the tooth and restorations, making it susceptible to plaque accumulation. The purpose of this study was to investigate the effect of 5 s and 10 s air-abrasion of calcium carbonate on surface roughness (Ra) of enamel, nanofill, and microhybrid resin-composites and the effect of post-polishing with two-step rubber- (RP) or one-step brush polisher (BP) to re-establish the surface smoothness. Surface topography was visualized by scanning-electron-microscopy. The quantitative measurement of the Ra was carried out with atomic-force-microscopy. Air-abrasion for 10 s decreased the Ra of enamel as a result of abrasion of the natural surface texture. Post-polishing with RP after 10 s air-abrasion did not change the Ra or BP; however, Ra was increased significantly by scratching the surface. Air-abrasion increased the Ra of resin composites significantly, irrespective of the application time. While RP provided a similarly smooth surface to the control in the case of microhybrid resin composite, BP increased the Ra significantly. The Ra for the control group of the nanofill-resin composite was initially high, which was further increased by air-abrasion. RP and BP re-established the initial Ra with deeper and shallower scratches after BP. Both the material and treatment type showed a large effect on Ra.

Investigation of synapses in the cortical white matter in human temporal lobe epilepsy.

Temporal lobe epilepsy (TLE) is one of the most common focal pharmacotherapy-resistant epilepsy in adults. Previous studies have shown significantly higher numbers of neurons in the neocortical white matter in TLE patients than in controls. The aim of this work was to investigate whether white matter neurons are part of the neuronal circuitry. Therefore, we studied the distribution and density of synapses in surgically resected neocortical tissue of pharmacotherapy-resistant TLE patients. Neocortical white matter of temporal lobe from non-epileptic patients were used as controls. Synapses and neurons were visualized with immunohistochemistry using antibodies against synaptophysin and NeuN, respectively. The presence of synaptophysin in presynaptic terminals was verified by electron microscopy. Quantification of immunostaining was performed and the data of the patients' cognitive tests as well as clinical records were compared to the density of neurons and synapses. Synaptophysin density in the white matter of TLE patients was significantly higher than in controls. In TLE, a significant correlation was found between synaptophysin immunodensity and density of white matter neurons. Neuronal as well as synaptophysin density significantly correlated with scores of verbal memory of TLE patients. Neurosurgical outcome of TLE patients did not significantly correlate with histological data, although, higher neuronal and synaptophysin densities were observed in patients with favorable post-surgical outcome. Our results suggest that white matter neurons in TLE patients receive substantial synaptic input and indicate that white matter neurons may be integrated in epileptic neuronal networks responsible for the development or maintenance of seizures.

Etiology-related Degree of Sprouting of Parvalbumin-immunoreactive Axons in the Human Dentate Gyrus in Temporal Lobe Epilepsy.

In the present study, we examined parvalbumin-immunoreactive cells and axons in the dentate gyrus of surgically resected tissues of therapy-resistant temporal lobe epilepsy (TLE) patients with different etiologies. Based on MRI results, five groups of patients were formed: (1) hippocampal sclerosis (HS), (2) malformation of cortical development, (3) malformation of cortical development + HS, (4) tumor-induced TLE, (5) patients with negative MRI result. Four control samples were also included in the study. Parvalbumin-immunoreactive cells were observed mostly in subgranular location in the dentate hilus in controls, in tumor-induced TLE, in malformation of cortical development and in MR-negative cases. In patients with HS, significant decrease in the number of hilar parvalbumin-immunoreactive cells and large numbers of ectopic parvalbumin-containing neurons were detected in the dentate gyrus' molecular layer. The ratio of ectopic/normally-located cells was significantly higher in HS than in other TLE groups. In patients with HS, robust sprouting of parvalbumin-immunoreactive axons were frequently visible in the molecular layer. The extent of sprouting was significantly higher in TLE patients with HS than in other groups. Strong sprouting of parvalbumin-immunoreactive axons were frequently observed in patients who had childhood febrile seizure. Significant correlation was found between the level of sprouting of axons and the ratio of ectopic/normally-located parvalbumin-containing cells. Electron microscopy demonstrated that sprouted parvalbumin-immunoreactive axons terminate on proximal and distal dendritic shafts as well as on dendritic spines of granule cells. Our results indicate alteration of target profile of parvalbumin-immunoreactive neurons in HS that contributes to the known synaptic remodeling in TLE.

[Postoperative outcome of surgical interventions for epilepsy between 2005 and 2016 at the Epilepsy Center of Pécs]. / Epilepsziasebészeti beavatkozások eredményei a Pécsi Epilepszia Centrumban 2005 és 2016 között.

INTRODUCTION: Epilepsy as a chronic, severe neurologic disease significantly influences the quality of life of the epileptic patients. In candidates well selected for surgery, the seizure freedom is realistically achievable, and the quality of life can be further improved with complex individual rehabilitation. AIM: We aimed to evaluate the postoperative outcome of patients who underwent epilepsy surgery between 2005 and 2016 at the Epilepsy Center at Pécs. METHOD: We evaluated seizure status at regular follow-up visits after surgery and the quality of life using questionnaires focusing on employment and social status. RESULTS: 76% of the 72 patients who underwent surgical resection for epilepsy were free from disabling seizures , and 10% had rare disabling seizures (almost seizure-free), 7% experienced worthwhile improvement and 7% had no worthwhile improvement. Comparing the employment status of patients free from disabling seizures to patients not free from disabling seizures, we found that the employment status is significantly influenced by seizure freedom (p<0.01, Fisher's exact test). While 67% of seizure-free patients were employed, only 19% of patients not free from disabling seizures were hired. CONCLUSION: Our results resemble the international tendencies and success rate, proving epilepsy surgery as an available, valid and effective treatment in well selected patients. Orv Hetil. 2019; 160(7): 270-278.

Electron Microscopic Analysis of Hippocampal Axo-Somatic Synapses in a Chronic Stress Model for Depression.

Stress can alter the number and morphology of excitatory synapses in the hippocampus, but nothing is known about the effect of stress on inhibitory synapses. Here, we used an animal model for depression, the chronic mild stress model, and quantified the number of perisomatic inhibitory neurons and their synapses. We found reduced density of parvalbumin-positive (PV+) neurons in response to stress, while the density of cholecystokinin-immunoreactive (CCK+) neurons was unaffected. We did a detailed electron microscopic analysis to quantify the frequency and morphology of perisomatic inhibitory synapses in the hippocampal CA1 area. We analyzed 1100 CA1 pyramidal neurons and 4800 perisomatic terminals in five control and four chronically stressed rats. In the control animals we observed the following parameters: Number of terminals/soma = 57; Number of terminals/100 µm cell perimeter = 10; Synapse/terminal ratio = 32%; Synapse number/100 terminal = 120; Average terminal length = 920nm. None of these parameters were affected by the stress exposure. Overall, these data indicate that despite the depressive-like behavior and the decrease in the number of perisomatic PV+ neurons in the light microscopic preparations, the number of perisomatic inhibitory synapses on CA1 pyramidal cells was not affected by stress. In the electron microscope, PV+ neurons and the axon terminals appeared to be normal and we did not find any apoptotic or necrotic cells. This data is in sharp contrast to the remarkable remodeling of the excitatory synapses on spines that has been reported in response to stress and depressive-like behavior. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.

The Harvard organic photovoltaic dataset.

The Harvard Organic Photovoltaic Dataset (HOPV15) presented in this work is a collation of experimental photovoltaic data from the literature, and corresponding quantum-chemical calculations performed over a range of conformers, each with quantum chemical results using a variety of density functionals and basis sets. It is anticipated that this dataset will be of use in both relating electronic structure calculations to experimental observations through the generation of calibration schemes, as well as for the creation of new semi-empirical methods and the benchmarking of current and future model chemistries for organic electronic applications.

Characterization of neurons in the cortical white matter in human temporal lobe epilepsy.

The aim of the present work was to characterize neurons in the archi- and neocortical white matter, and to investigate their distribution in mesial temporal sclerosis. Immunohistochemistry and quantification of neurons were performed on surgically resected tissue sections of patients with therapy-resistant temporal lobe epilepsy. Temporal lobe tissues of patients with tumor but without epilepsy and that from autopsy were used as controls. Neurons were identified with immunohistochemistry using antibodies against NeuN, calcium-binding proteins, transcription factor Tbr1 and neurofilaments. We found significantly higher density of neurons in the archi- and neocortical white matter of patients with temporal lobe epilepsy than in that of controls. Based on their morphology and neurochemical content, both excitatory and inhibitory cells were present among these neurons. A subset of neurons in the white matter was Tbr-1-immunoreactive and these neurons coexpressed NeuN and neurofilament marker SMI311R. No colocalization of Tbr1 was observed with the inhibitory neuronal markers, calcium-binding proteins. We suggest that a large population of white matter neurons comprises remnants of the subplate. Furthermore, we propose that a subset of white matter neurons was arrested during migration, highlighting the role of cortical maldevelopment in epilepsy associated with mesial temporal sclerosis.

A quinazoline-derivative compound with PARP inhibitory effect suppresses hypertension-induced vascular alterations in spontaneously hypertensive rats.

AIMS: Oxidative stress and neurohumoral factors play important role in the development of hypertension-induced vascular remodeling, likely by disregulating kinase cascades and transcription factors. Oxidative stress activates poly(ADP-ribose)-polymerase (PARP-1), which promotes inflammation and cell death. We assumed that inhibition of PARP-1 reduces the hypertension-induced adverse vascular changes. This hypothesis was tested in spontaneously hypertensive rats (SHR). METHODS AND RESULTS: Ten-week-old male SHRs and wild-type rats received or not 5mg/kg/day L-2286 (a water-soluble PARP-inhibitor) for 32 weeks, then morphological and functional parameters were determined in their aortas. L-2286 did not affect the blood pressure in any of the animal groups measured with tail-cuff method. Arterial stiffness index increased in untreated SHRs compared to untreated Wistar rats, which was attenuated by L-2286 treatment. Electron and light microscopy of aortas showed prominent collagen deposition, elevation of oxidative stress markers and increased PARP activity in SHR, which were attenuated by PARP-inhibition. L-2286 treatment decreased also the hypertension-activated mitochondrial cell death pathway, characterized by the nuclear translocation of AIF. Hypertension activated all three branches of MAP-kinases. L-2286 attenuated these changes by inducing the expression of MAPK phosphatase-1 and by activating the cytoprotective PI-3-kinase/Akt pathway. Hypertension activated nuclear factor-kappaB, which was prevented by PARP-inhibition via activating its nuclear export. CONCLUSION: PARP-inhibition has significant vasoprotective effects against hypertension-induced vascular remodeling. Therefore, PARP-1 can be a novel therapeutic drug target for preventing hypertension-induced vascular remodeling in a group of patients, in whom lowering the blood pressure to optimal range is harmful or causes intolerable side effects.

Glucocorticoid receptor protein expression in human hippocampus; stability with age.

The glucocorticoid receptor (GR) exerts numerous functions in the body and brain. In the brain, it has been implicated, amongst others, in feedback regulation of the hypothalamic-pituitary-adrenal axis, with potential deficits during aging and in depression. GRs are abundantly expressed in the hippocampus of rodent, except for the Ammon's horn (CA) 3 subregion. In rhesus monkey however, GR protein was largely absent from all hippocampal subregions, which prompted us to investigate its distribution in human hippocampus. After validation of antibody specificity, we investigated GRα protein distribution in the postmortem hippocampus of 26 human control subjects (1-98 years of age) and quantified changes with age and sex. In contrast to monkey, abundant GR-immunoreactivity was present in nuclei of almost all neurons of the hippocampal CA subfields and dentate gyrus (DG), although neurons of the CA3 subregion displayed lower levels of immunoreactivity. Colocalization with glial fibrillary acidic protein confirmed that GR was additionally expressed in approximately 50% of the astrocytes in the CA regions, with lower levels of colocalization (approximately 20%) in the DG. With increased age, GR expression remained stable in the CA regions in both sexes, whereas a significant negative correlation was found with age only in the DG of females. Thus, in contrast to the very low levels previously reported in monkey, GR protein is prominently expressed in human hippocampus, indicating that this region can form an important target for corticosteroid effects in human.

Impaired myelination of the human hippocampal formation in Down syndrome.

Myelination is considered as one of the last steps of neuronal development and is essential to the physiologically matured function of afferent and efferent pathways. In the present study, myelin formation was examined in the human fetal, postnatal and adult hippocampal formation in Down syndrome and in age-matched controls with immunohistochemistry detecting a protein component of the myelin sheath, the myelin basic protein synthesized by oligodendroglial cells. Myelination is mainly a postnatal event in the hippocampal formation of both healthy controls and in patients with Down syndrome. In patients with Down syndrome the sequence of myelination of the hippocampal formation followed a similar developmental pattern to that in controls. However, myelin formation was generally delayed in Down syndrome compared to age-matched controls. In addition, in the hilus of the dentate gyrus a decreased density of myelinated axons was detected from the start of myelination until adulthood. The majority of local axons (mossy fibers) are not myelinated in the hilar region and myelinated fibers arriving in the hilus come mainly from the subcortical septal nuclei. Since intact septo-hippocampal connections are necessary for memory formation, we hypothesize that decreased myelination in the hilus may contribute to the mental retardation of Down syndrome patients.

Vesicular zinc regulates the Ca2+ sensitivity of a subpopulation of presynaptic vesicles at hippocampal mossy fiber terminals.

Synaptic vesicles segregate into functionally diverse subpopulations within presynaptic terminals, yet there is no information about how this may occur. Here we demonstrate that a distinct subgroup of vesicles within individual glutamatergic, mossy fiber terminals contain vesicular zinc that is critical for the rapid release of a subgroup of synaptic vesicles during increased activity in mice. In particular, vesicular zinc dictates the Ca(2+) sensitivity of release during high-frequency firing. Intense synaptic activity alters the subcellular distribution of zinc in presynaptic terminals and decreases the number of zinc-containing vesicles. Zinc staining also appears in endosomes, an observation that is consistent with the preferential replenishment of zinc-enriched vesicles by bulk endocytosis. We propose that functionally diverse vesicle pools with unique membrane protein composition support different modes of transmission and are generated via distinct recycling pathways.

Degree and pattern of calbindin immunoreactivity in granule cells of the dentate gyrus differ in mesial temporal sclerosis, cortical malformation- and tumor-related epilepsies.

A loss of calbindin immunoreactivity in granule cells of the hippocampal dentate gyrus is a characteristic feature of temporal lobe epilepsy with hippocampal sclerosis. Whether decreased calbindin expression is unique to the hippocampal sclerosis associated with cryptogenic temporal lobe epilepsy, or also occurs in tumor- or malformation-related epilepsy, is unknown. We show that calbindin immunoreactivity in granule cells has been decreased in epilepsy regardless of its etiology. In cases of cortical malformations or hippocampal sclerosis, calbindin immunoreactivity was undetectable in most granule cells. In tumor-related resections, in patients who had a long history of epileptic seizures, calbindin was detected only in one-third of granule cells. Regardless of etiology, calbindin expression correlated with age of onset and with duration of the epilepsy. In contrast to tumor-induced epilepsy, where calbindin-immunoreactive granule cells were equally distributed in the granule cell layer, in hippocampal sclerosis and malformation-related epilepsy, two-thirds of calbindin-immunoreactive granule cells were located in the outer half and only one-third in the inner half of the layer. Developmentally, granule cells at the border of the molecular layer are ontogenetically the oldest, and those at the border of the hilus are the youngest. The reduction of calbindin immunoreactivity in ontogenetically younger granule cells highlights the deleterious effect of early occurring epilepsy and initial early precipitating injury, including febrile seizures that may substantially affect developing immature granule cells, but less the earlier born matured ones.

Myelination in the human hippocampal formation from midgestation to adulthood.

Myelination, one of the last steps of neuronal development, was examined in the human fetal and postnatal hippocampal formation using immunohistochemistry to detect a protein component of the myelin sheath, the myelin basic protein synthesized by oligodendroglial cells. Myelin basic protein-immunoreactive oligodendroglial cells were first seen at the 20th gestational week in the fimbria fornicis and in the alveus. Between the 21st and 35th weeks, myelinated axons also appeared in the fimbria fornicis. At the age of 39 gestational weeks, short and thin myelinated fibers were present in the fimbria, in the alveus, and less so in the stratum oriens of the hippocampus, while the first oligodendroglial cells appeared in the stratum lacunosum-moleculare and in the hilus. By the 2nd postnatal week myelinated fibers appeared in the stratum lacunosum-moleculare of Ammon's horn. At the 3rd month, myelination was strong in the alveus, moderate in the strata oriens, lacunosum-moleculare and radiatum of Ammon's horn, while only a small number of myelinated fibers were detected in the hilus. By the 5th month, the first oligodendroglial cells were detected in the molecular layer of the dentate gyrus. Myelination continued in the following years, particularly in the dentate gyrus, where even at the age of 11 years the density of myelinated fibers did not reach the adult level. It appears that the first myelinated axons belong to the long-projecting large hippocampal pyramidal cells and/or to their subcortical and cortical afferents. The sequence of myelination follows the known developmental pattern of hippocampal afferent and efferent pathways, and the prolonged myelination might be a factor in the prolonged functional maturation of hippocampal circuitry.

Survival of mossy cells of the hippocampal dentate gyrus in humans with mesial temporal lobe epilepsy.

OBJECT: Hippocampal sclerosis can be identified in most patients with mesial temporal lobe epilepsy (TLE). Surgical removal of the sclerotic hippocampus is widely performed to treat patients with drug-resistant mesial TLE. In general, both epilepsy-prone and epilepsy-resistant neurons are believed to be in the hippocampal formation. The hilar mossy cells of the hippocampal dentate gyrus are usually considered one of the most vulnerable types of neurons. The aim of this study was to clarify the fate of mossy cells in the hippocampus in epileptic humans. METHODS: Of the 19 patients included in this study, 15 underwent temporal lobe resection because of drug-resistant TLE. Four patients were used as controls because they harbored tumors that had not invaded the hippocampus and they had experienced no seizures. Histological evaluation of resected hippocampal tissues was performed using immunohistochemistry. RESULTS: Mossy cells were identified in the control as well as the epileptic hippocampi by using cocaine- and amphetamine-regulated transcript peptide immunohistochemistry. In most cases the number of mossy cells was reduced and thorny excrescences were smaller in the epileptic hippocampi than in controls; however, there was a significant loss of pyramidal cells and a partial loss of granule cells in the same epileptic hippocampi in which mossy cell loss was apparent. The loss of mossy cells could be correlated with the extent of hippocampal sclerosis, patient age at seizure onset, duration of epilepsy, and frequency of seizures. CONCLUSIONS: In many cases large numbers of mossy cells were present in the hilus of the dentate gyrus when most pyramidal neurons of the CA1 and CA3 areas of the Ammon's horn were lost, suggesting that mossy cells may not be more vulnerable to epileptic seizures than the hippocampal pyramidal neurons.

Ontogeny of calbindin immunoreactivity in the human hippocampal formation with a special emphasis on granule cells of the dentate gyrus.

Calbindin (CB) is a calcium-binding protein that is present in principal cells as well as in interneurons of the hippocampal formation of various species including humans. Studies with transgenic mice revealed that CB is essential for long-term potentiation and synaptic plasticity which are the cellular basis of learning and memory. In a previous study we have shown that CB expression in granule cells of the dentate gyrus correlates with the functional maturation of the hippocampal formation in the rat. In the present study we examined the ontogeny of CB using immunohistochemistry in the human hippocampal formation paying special attention to the granule cells of the dentate gyrus. As early as the 14(th) week of gestation (GW), CB was being expressed by pyramidal cells of CA1-3 regions in the deepest cell rows of the pyramidal layer towards the ventricular zone. Later, CB sequentially appears in more superficial cell rows. After midgestation, CB disappears from CA3 pyramidal neurons. Expression of CB by granule cells starts at the 22(nd)-23(rd) GW, first by the most superficial neurons of the ectal end of the dorsal blade. At the 24(th) GW, CB is expressed by granule cells of the crest and medial portion of the ventral blade whereas later the entire ventral blade revealed CB immunoreactivity. At term, and in the first few postnatal months, CB-immunoreaction is detected in granule cells of both blades except for those neurons in the deepest cell rows at the hilar border. At around 2-3 years of age, all granule cells of the entire cell layer are CB-immunoreactive. Axons of granule cells, the mossy fibers, start to express CB around the 30(th) GW in stratum lucidum of CA3a. With further development, CB is expressed in CA3b and c, as well as in the hilus. An adult-like pattern of CB-immunoreactivity could be observed at 11 years of age. Our results indicate that (i) CB is expressed by hippocampal pyramidal cells a few weeks before midgestation; (ii) similarly to rodents, migration of postmitotic human hippocampal pyramidal cells follows the inside-out gradient; (iii) CB was expressed transiently in pyramidal cells of the CA3 area of the human hippocampus; (iv) granule cells of the dentate gyrus start to express CB as early as midgestation; (v) maturation and migration of human granule cells follow the outside-in migrational gradient described in rodents and non-human primates; (vi) CB-immunoreactivity in the axon terminals of granule cells could be observed a few weeks before birth with a long-lasting increase in staining intensity postnatally; (vii) the maturation pattern of the CB-positive mossy fiber system suggests that the development of connectivity and the mature topographical termination pattern between dentate gyrus and the CA3 area of Ammon's horn in humans resembles that previously described for rodents; (viii) the dorsal-ventral delay in development may explain the topography of neuropathologic alterations of the granule cell layer found in temporal lobe epilepsy related to febrile seizures.

Crystal-storing histiocytosis associated with only one of two consecutive, but genetically unrelated B-cell lymphomas.

A localized crystal-storing histiocytosis (CSH) making the underlying marginal zone lymphoma (MZL) hardly discernible microscopically is described. Image analysis of the hyper electron dense crystals localized light microscopically in swollen histiocytic cells exhibited a major equatorial periodicity of 6.6 nm. Rarely, crystals of this type were detected within plasma cells, but were always surrounded by smooth membrane in contrast to Russell bodies. IgM/lambda restriction and VH3-21*02, DH4-17*01, JH4*02 gene usage were detected behind the lesion. Within 26 months, a genetically unrelated lymphoma of CD5-CD20-CD23-positive phenotype with a different VH1-24*01, DH2-21*02, JH2*01 heavy chain rearrangement, but with the same light chain gene usage, was identified without CSH. This might indicate that the unique condition responsible for the crystal formation is likely to rely on the sequence of the first clonally rearranged heavy chain exhibiting much higher CDRIII pI value (6.0) than the average.

A correlative light and electron microscopic study of postnatal myelination in the murine corpus callosum.

Oligodendroglial cells differ in their ultrastructural appearance depending on their myelin producing and maintaining activity. To better understand the relationship between light and electron microscopic features of myelination, myelin formation in the corpus callosum was studied in young postnatal mice. Immunostaining for myelin basic protein (MBP), which has an important role in myelin compaction, was compared with conventional Luxol Fast Blue myelin staining and with electron microscopic images of unlabeled tissue. MBP-immunostaining labeled a few oligodendroglial cells at postnatal day (P)3, and a few axons at P7 in the corpus callosum, below the fronto-parietal somatosensory cortex. By P10 there were more myelinated axons below the somatosensory cortex and the first MBP-immunoreaction appeared in the cingulum: labeling appeared even later in the remaining areas of corpus callosum. Electron microscopy revealed numerous medium oligodendroglial cells at P7 in the corpus callosum, below the somatosensory cortex with the first sign of myelination at P10. By P14, there were numerous myelin sheaths with loosely built structure, and the number of myelin sheaths increased continuously thereafter. However, even as late as P28, the presence of both thick, compact and thin, loosely structured myelin sheaths in the same section suggested ongoing myelination. With Luxol Fast Blue myelin staining was first observed in the corpus callosum relatively late, at P14. Areal differences in myelination of the corpus callosum, seen with MBP-immunohistochemistry, indicate that myelin formation follows cortical maturation rather than the rostro-caudal developmental growth of the corpus callosum. Myelination of the afferent and efferent fibers within the cortical areas seems to follow the inside-out maturational pattern of cortical neurons, with the first myelinated axons always appearing in layers V-VI. In addition to the known neuronal and astroglial factors that regulate myelin formation by oligodendroglial cells, we suggest that these cells and their myelin covering may also influence axonal maturation. Light microscopic data obtained with MBP-immunohistochemistry correlates well with electron microscopic observations but not with Luxol Fast Blue staining which reveals myelinated axons only relatively late in development. Therefore, both MBP-immunostaining and electron microscopy are useful, alone or in combination, for the detection of myelination, demyelination as well as remyelination processes in animal models and also in humans.

Evidence for the expression of parathyroid hormone 2 receptor in the human brainstem.

BACKGROUND AND PURPOSE: The parathyroid hormone 2 receptor (PTH2R) is a G protein coupled receptor. Pharmacological and anatomical evidence suggests that the recently identified tuberoinfundibular peptide of 39 residues is, and parathyroid hormone and parathyroid hormone-related peptide are not, its endogenous ligand. Initial functional studies suggest that the PTH2R is involved in the regulation of viscerosensory information processing. As a first step towards clinical applications, herein we describe the presence of the PTH2R in the human brainstem. MATERIAL AND METHODS: Total RNA was isolated from postmortem human cortical and brainstem samples for RT-PCR. Good quality RNA, as assessed on formaldehyde gel, was reverse transcribed. The combined cDNA products were used as template in PCR reactions with primer pairs specific for the human PTH2R. In addition, PTH2R immunolabelling was performed on free floating sections of the human medulla oblongata using fluorescent amplification immunochemistry. RESULTS: Specific bands in the RT-PCR experiments and sequencing of PCR products demonstrated the expression of PTH2R mRNA in the human brainstem. A high density of PTH2R-immunoreactive fibers was found in brain regions of the medulla oblongata including the nucleus of the solitary tract, the spinal trigeminal nucleus, and the dorsal reticular nucleus of the medulla. CONCLUSION: Independent demonstration of the presence of PTH2R mRNA and immunoreactivity supports the specific expression of the PTH2R in the human brainstem. The distribution of PTH2R-immunoreactive fibers in viscerosensory brain regions is similar to that reported in mouse and rat suggesting a similar role of the PTH2R in human as in rodents. This finding will have important implications when experimental data obtained on the function of the TIP39-PTH2R neuromodulator system in rodents are to be utilized in human.

Calretinin expression in hilar mossy cells of the hippocampal dentate gyrus of nonhuman primates and humans.

Mossy cells, the major excitatory neurons of the hilus of the dentate gyrus constitutively express calretinin in several rodent species, including mouse and hamster, but not in rats. Several studies suggest that mossy cells of the monkey dentate gyrus are calretinin-positive, but others have reported mossy cells in monkeys to be devoid of detectable calretinin-like immunoreactivity. In the present study, the hilar region was investigated throughout the entire longitudinal extent of the hippocampal dentate gyrus in both Old World and New World monkeys, as well as in humans. In the examined four monkey species, mossy cells were found to be calretinin-positive at the uncal pole and at variable length within the main body of the dentate gyrus but not in the tail part. The associational pathway, formed by axons of mossy cells in the inner dentate molecular layer was calretinin-positive in more caudal sections, suggesting that mossy cell axon terminals may contain calretinin, whereas mossy cell somata may contain calretinin in a concentration too low to be detected by immunocytochemistry. In contrast, human mossy cells appear to be devoid of calretinin immunoreactivity in both their somata and their axon terminals. Taken together, mossy cells of nonhuman primates and humans exhibit different expression pattern for calretinin whereas they show similarities in neurochemical content, such as the cocaine and amphetamine-related transcript peptide.