Anatomic relationships of the human nucleus paragigantocellularis lateralis: a DiI labeling study.

The nucleus paragigantocellularis lateralis (PGL) is located in the rostral ventrolateral medulla (RVLM), a brainstem region that regulates homeostatic functions, such as blood pressure and cardiovascular reflexes, respiration. central chemosensitivity and pain. In the present study, we examined anatomic relationships of the human nucleus paragigantocellularis lateralis using a bidirectional lipophilic fluorescent tracer, 1,1'-dioctadecyl-3,3.3',3'-tetramethylindocarbocyanine perchlorate (DiI), in nine postmortem human fetal midgestational brainstems. The areas which were labeled by diffusion of DiI from the nucleus paragigantocellularis lateralis included the arcuate nucleus (ARC) of the medulla, caudal raphe (nucleus raphe obscurus and pallidus), hilum and amiculum of the inferior olive, bilateral "reticular formation" (including the nucleus paragigantocellularis lateralis, nucleus gigantocellular-is and the intermediate reticular zone (IRZ)). vestibular and cochlear nuclei, cells and fibers at the floor of the fourth ventricle with morphologic features of tanycytes, parabrachial nuclei (PBN), medial lemniscus, lateral lemniscus, inferior cerebellar peduncle and cerebellar white matter, central tegmental tract, and the capsule of the red nucleus. This pattern of DiI labeling bears many similarities with the pattern of connections of the nucleus paragigantocellularis lateralis previously demonstrated by tract-tracing methods in experimental animals, and is consistent with the role of the nucleus paragigantocellularis lateralis in central regulation of homeostatic functions. In contrast to the animal studies, however, we did not demonstrate connections of the nucleus paragigantocellularis lateralis with the nucleus of the tractus solitarius (nTS) (only connections with the rostral subdivision were examined), locus coeruleus, or the periaqueductal gray (PAG) in the human midgestational brainstem. In our previous studies, six medullary areas showed reduced serotonin receptor binding in a subset of victims of sudden infant death syndrome (SIDS). The present study demonstrated DiI labeling in all of these six areas, suggesting that they are interconnected.

Cystic malformation of the posterior cerebellar vermis in transgenic mice that ectopically express Engrailed-1, a homeodomain transcription factor.

In WEXPZ-En-1 transgenic mice, Engrailed-1, a homeodomain-containing transcription factor, is ectopically expressed in the developing brain under control of the Wnt-1 enhancer. En-1 is a developmental regulatory control gene which has an essential role in the formation of the midbrain and cerebellum. Approximately 28% of WEXPZ-En-1 + mice develop cystic malformations of the posterior lobe of the cerebellar vermis, fourth ventricular dilatation, and postnatal hydrocephalus. These anatomic features are also found among the spectrum of posterior fossa malformations in humans. Expression characteristics of the WEXP transgene suggest that the neuropathology observed in WEXPZ-En-1+ mice stems from overexpression of En-1 during fetal and neonatal phases of cerebellar development. These observations raise the possibility that abnormal regulation of Engrailed genes, or targets of Engrailed, may be involved in the pathogenesis of cystic central nervous system malformations of the posterior fossa in humans.

3-Dimensional anatomic relationship of serotonergic and muscarinic receptor binding in the pontine reticular formation of the human infant brainstem.

Cholinergic and serotonergic neurons of the rostral pontine reticular formation have been implicated by animal studies in the modulation of sleep and waking. To define better the spatial relationships between muscarinic and serotonergic receptor binding in the rostral human brainstem, we used 3-dimensional computer reconstructions of serial autoradiographs generated with radioligands to muscarinic and serotonergic receptors. Receptor binding was assessed in a series of 9 human infants, and 3-dimensional reconstructions were performed in a representative infant at 53 postconceptional weeks. The computer reconstructions demonstrated a 3-dimensional distinct pattern in the rostral pontine reticular formation, with high (3H)lysergic acid diethylamide binding to serotonin receptors in the median raphe nucleus flanked by paramedian bands of high (3H)quinuclidinyl benzilate binding to muscarinic cholinergic receptors in the medial nucleus pontis oralis. Based upon comparisons to animal data, we suggest that the muscarinic-serotonergic pattern of receptor binding in the rostral pontine reticular formation represents part of the neurochemical organization of the circuitry involved in the modulation of rapid eye movement (REM) sleep in humans.

Anatomic relationships of the human arcuate nucleus of the medulla: a DiI-labeling study.

The arcuate nucleus (ARC) at the ventral surface of the human medulla has been historically considered a precerebellar nucleus. More recently, it has been implicated in central chemoreception, cardiopulmonary coupling and blood pressure responses. A deficiency of the ARC has been reported in a subset of putative human developmental disorders of ventilatory function. To investigate anatomic relationships of the ARC with brainstem regions involved in cardiorespiratory control, we applied crystals of DiI, a lipophilic dye which labels cells and cell processes by lateral diffusion along cell membranes, to 23 paraformaldehyde-fixed human fetal brainstems at 19 to 22 weeks postconceptional age. After 7 to 15.5 months diffusion, serial frozen sections were examined by florescence microscopy. DiI diffusion from the ARC labeled fibers and cell bodies in the medullary raphé, and the external arcuate fibers. Diffusion from the medullary raphé [corrected] labeled the reticular formation, medullary raphé, and the ARC. Diffusion from the pyramid and the basis pontis (negative control) labeled the corticospinal tract, with no labeling of the medullary raphé or ARC. The results suggest the existence of cellular connections between the ARC and the caudal raphé, a region implicated in cardiorespiratory control.

Expression of the homeobox-containing genes EN1 and EN2 in human fetal midgestational medulla and cerebellum.

Homeobox-containing genes En-1 and En-2 have been implicated in the control of pattern formation during development of the central nervous system in experimental animals. In order to determine whether the expression of homologous human EN genes can be used as a developmental genetic marker of the arcuate nucleus of the medulla (a putative precerebellar nucleus that shows developmental deficiency in a subset of sudden infant death syndrome [SIDS]), we performed in situ hybridization with human EN1 and EN2 RNA probes in human fetal midgestational medulla and cerebellum (18-21 weeks gestational age, n=4). Expression of EN genes was demonstrated in all neuronal groups of the medulla and throughout the cerebellum. The RNA signal for both EN1 and EN2 was strongest in the cerebellar granule cell layers, white matter of the vermis and flocculus, inferior olive, arcuate nucleus, caudal raphe nuclei, corpus pontobulbare and nucleus ambiguus. Most of the structures that showed the strongest EN signal originate in the rhombic lip. Some of these structures are functionally interconnected, and show pathologic changes in the syndrome of infantile olivopontocerebellar hypoplasia/atrophy. Strong expression of EN signal in the arcuate nucleus could be used as a genetic marker of this nucleus in further developmental studies of the arcuate nucleus in SIDS. Although EN expression is not specific to the arcuate nucleus or to the rhombic lip derivatives, our results suggest that rhombic lip derivatives have the highest levels of EN RNA message among the medullary structures at midgestation.

Immunohistochemically identifiable tissue plasminogen activator in cavernous angioma: mechanism for re-hemorrhage and lesion growth.

The mechanisms governing growth of cavernous angiomas of the brain and their propensity to hemorrhage remain unknown. Repetitive hemorrhage with neovascularization during clot organization and maturation of new vessels into a larger cavernous angioma has been hypothesized as one mechanism. This hypothesis is largely based on the histopathological similarity between the organizing clot surrounding cavernous malformations and the organizing phase of the membranes surrounding chronic subdural hematoma. The presence of tissue plasminogen activator (TPA) in the vascular endothelium of vessels contained within chronic subdural membranes has been used to argue that an intrinsic thrombolytic process is responsible, in part, for rebleeding within chronic subdural cavities. By analogy, we sought to identify whether TPA is located in tissues in and around cavernous angiomas. Cavernous malformations, surgically removed and pathologically confirmed by standard staining techniques, were immunohistochemically stained for TPA. Eleven of thirteen lesions (85%) studied contained vascular endothelial cells which stained for TPA. Of the 2 lesions which did not contain TPA, 1 was non-hemorrhagic and calcified; 7 of 11 (64%) lesions which contained TPA presented clinically with hemorrhage. These data support the hypothesis that a local thrombolytic process may be responsible for the frequent hemorrhagic nature of cavernous angiomas. Alternatively, since local elaboration of TPA is common to both chronic subdural membranes and cavernous angiomas, this finding may represent a more global characteristic of fibrinolytic homeostasis in cerebral tissues.

Giant cell ependymoma of the filum terminale. A report of two cases.

We describe two histologically unusual cases of ependymoma of the filum terminale. Both tumors occurred in 14-year-old boys. An intradural encapsulated mass attached to the filum terminale was demonstrated radiologically in both cases and totally resected at surgery. In case 1 the neoplasm was uniformly composed of pleomorphic giant cells and was without perivascular pseudorosettes or myxopapillary changes. Case 2 was a myxopapillary ependymoma with multiple foci of pleomorphic giant cells. Neither tumor had prominent mitotic activity, necrosis, or endothelial proliferation. Both tumors were immunopositive for cytokeratin and glial fibrillary acidic protein. Ultrastructural features included basal laminae, interdigitating cell processes, microvilli, cilia, intercellular junctions, and cytoplasmic intermediate filaments. Cytogenetic analysis in case 1 showed a hypodiploid karyotype with monosomy of chromosomes 1, 10, 14, 16, 20, and 22. We interpret both tumors as most consistent with a variant of ependymoma. Because of the unique gigantocellular light microscopic appearance of the entire tumor in case 1, we propose classifying this tumor as a new morphologic subtype: giant cell ependymoma of the filum terminale. The combination of gigantocellular and myxopapillary features in case 2 supports a histogenetic relationship between giant cell ependymoma and myxopapillary ependymoma.

Enteroaggregative Escherichia coli associated with an outbreak of diarrhoea in a neonatal nursery ward.

Over a 9-day period in February 1995, 16 newborn babies (age range 2-11 days) and 3 infants (24, 47 and 180 days of age) in a neonatal nursery ward developed diarrhoea accompanied by pyrexia and weight loss. Known enteropathogens were not detected in their stools but Escherichia coli displaying aggregative adherence to HEp-2 cells (enteroaggregative E. coli) were found in 12 (63%) ill infants and in none of 5 well neonates (P = 0.02). The illness lasted 3-9 days (mean 5.2) in 16 babies, whereas in 3 neonates it showed a protracted course of 18-20 days. The source of infection and the mode of transmission remained unclear. The outbreak isolates manifested properties common in this new group of diarrhoeagenic E. coli: mannose-resistant haemagglutination, haemolysis on blood agar, and clump formation in liquid culture medium. They belonged to the O4 E. coli serogroup and expressed multiple antibiotic resistance.

Developmental changes in [3H]lysergic acid diethylamide ([3H]LSD) binding to serotonin receptors in the human brainstem.

The ontogeny of serotonin receptors in the human brainstem is largely unknown, despite the putative roles of serotonin in neural development, synaptic transmission, brainstem modulation of vegetative functions, and clinical disorders of serotonergic function. This study provides baseline information about the quantitative distribution of [3H]LSD binding to serotonergic receptors (5-HT1A-1D, 5-HT2) in the human brainstem, from midgestation through maturity, with a focus upon early infancy. Brainstems were analyzed from 5 fetuses (19-25.5 weeks postconception), 5 infants (42-55.5 weeks postconception), and 3 mature individuals (4, 20, and 52 years). Tissue autoradiography was used with [3H]LSD for total serotonergic receptor binding and [3H]LSD and serotonin for nonspecific binding; computer-based quantitation was applied. The highest levels of [3H]LSD binding occurred prenatally throughout the brainstem. At all ages, the highest relative binding localized to the rostral raphe. A marked decline in [3H]LSD binding occurred between the midgestation and infancy in brainstem regions involved in control of cardiovascular function, respiration, and pain. The fetal peak in [3H]LSD binding to 5-HT receptors is consistent with a trophic role of serotonin in immature human brainstem, and a decrease, between midgestation and infancy, in serotonergic modulation of vegetative functions controlled by the brainstem.

Dark-rearing fails to affect the basal dendritic fields of layer 3 pyramidal cells in the kitten's visual cortex.

The development of the cat's visual cortex is incomplete at birth and is influenced by the cat's early visual experience. We have previously demonstrated that the basal dendritic fields of layer 3 pyramidal cells grow substantially during the first 5 weeks after birth and that stripe-rearing affects their orientation. In this paper we determined the effects on these dendritic fields of visual deprivation (dark-rearing) during the first 3 months of life. The visual cortices of both normally reared and dark-reared cats were impregnated by the Golgi method, sectioned in the tangential plane and counterstained. The basal dendritic fields of completely impregnated pyramidal cells from layer 3 were drawn with the aid of a camera lucida, and compared in terms of number and length of primary dendrites, branching, size, elongation, and distribution of dendritic field orientations. Surprisingly, we observed no significant differences in any parameter measured. Thus, although stripe-rearing can specifically alter the orientation of the dendritic fields of the layer 3 pyramidal cells, and dark-rearing has been shown by others to alter the size of layer 4 stellate cells, dark-rearing failed to affect the dendritic fields of layer 3 pyramidal cells.

Temporal evolution of neuropathologic changes in an immature rat model of cerebral hypoxia: a light microscopic study.

The sequential evolution of neuropathologic changes was studied in an immature model of cerebral hypoxia-ischemia. According, 7-day postnatal rats were subjected to unilateral common carotid artery ligation combined with 2 h of hypoxia (breathing in 8% oxygen) and their brains were examined by light microscopy at recovery intervals ranging from 0 to 3 weeks. Immediately following hypoxia, a large area with a pale staining border was noted occupying most of the cerebral hemisphere ipsilateral (IL) to the occluded common carotid artery; in approximately half of the brains the dorsomedial cortex of the contralateral (CL) hemisphere was also involved. Most neurons in the pale area had nuclei containing a coarse granular condensation of chromatin. Within a few hours, the majority of neurons in the IL hemisphere had developed pyknotic nuclei and clear or eosinophilic perikarya. After 24 h these changes had evolved in the majority of brains into coagulation necrosis (infarction) in the IL hemisphere and foci of selective neuronal necrosis in the CL cortex. Within a few days infarcts became partially cavitated, and by 3 weeks a smooth-walled cystic infarct had developed. Activated microglia/macrophages and reactive astrocytes were first seen at 4 and 24 h, respectively. No parenchymal neutrophilic infiltrate was seen at any time point.

Development of the dendritic fields of layer 3 pyramidal cells in the kitten's visual cortex.

The cat's visual cortex is immature at birth and undergoes extensive postnatal development. For example, cells of layers 2 and 3 do not complete migration until about 3 weeks after birth. Despite the importance of dendritic growth for synaptic and functional development, there have been few studies of dendritic development in the cat's visual cortex to correlate with numerous studies of functional and synaptic development. Accordingly, we used the Golgi method to study the development of the dendrites of layer 3 pyramidal cells in the visual cortex of a series of cats ranging in age from 2 days to 3 years. Blocks of visual cortex were impregnated by the Golgi-Kopsch method and sectioned in the tangential plane. Layer 3 pyramidal cells were drawn with a camera lucida and analyzed by Sholl diagrams and vector addition. In kittens < 1 week old, these cells were very immature, with only an apical dendrite and no basal dendrites. Basal dendrites appeared during the second week. By 2 weeks, all of the basal dendrites had emerged from the soma, but they had few branches and were tipped with growth cones. By 4 weeks, they had finished branching but continued to grow in length until, by 5 weeks, they reached their adult size. Examination of the basal dendritic fields in the tangential plane revealed that their dendritic fields were more elongated at 2 weeks than at later ages, perhaps because of their smaller size. The distribution of dendritic field orientations was uniform at all ages except 3 and 4 weeks, when there was a preponderance of fields oriented in the rostrocaudal direction. Because dendritic growth and branching occurred very rapidly over a period that precedes and overlaps with the peak periods of synaptogenesis and of sensitivity to the effects of early visual experience, they may depend on afferent visual activity. The early emergence of primary dendrites, however, suggests that this process is independent of afferent activity. The coincident timing of dendritic branching with the presence of dendritic growth cones suggests that branching may occur at growth cones.

Penicillamine-induced pseudoxanthoma elasticum-like skin changes requiring rhytidectomy.

A 42-year-old woman with pronounced skin laxity of her neck underwent a rhytidectomy and was found to have pseudoxanthoma elasticum-like changes of her skin. Her medical history was significant for Wilson's disease, requiring that she take penicillamine for 26 years. In patients on long-term penicillamine therapy, 20% to 33% will develop a dermatopathy. The drug has been used to alter scar formation in various surgical conditions. Penicillamine is known to alter cross-linking of elastin and collagen fibers. A review of the literature reveals other penicillamine-related dermatopathies that may present to the surgeon.

Extramedullary hematopoiesis in cerebellar hemangioblastoma.

Extramedullary hematopoiesis and paraneoplastic erythrocytosis are uncommon in cerebellar hemangioblastoma, and their concomitant occurrence has not been reported. In a study of 26 cases of hemangioblastoma, we found extramedullary hematopoiesis in 4 tumors; one was associated with erythrocytosis. The significance of this association and the possible histogenetic origin of extramedullary hematopoiesis in cerebellar hemangioblastoma are discussed.