Biomedical subjects

K Barami

Publications and source records attributed to K Barami.

10 recordsLinked to original sources

PubMed2000

Cellular transplantation and spinal cord injury.

Spinal cord injury is often characterized by immediate and irreversible loss of sensory and motor functions below the level of injury. Cellular transplantation in various experimental models of spinal cord injury has been used as a strategy for reducing deficits and improving functional recovery. The general strategy has been aimed at promoting regeneration of intrinsic injured axons with the development of alternative pathways that facilitate a partial functional connection. Other objectives of cellular transplantation studies have included replacement of lost cellular elements, alleviation of chronic pain, and modulation of the inflammatory response after injury. This review focuses on the cell types that have been used in spinal cord transplantation studies in the context of evolving biological perspectives, technological advances, and new therapeutic strategies and serves as a point of reference for future studies.

Animals↗

PubMed1998

Chemical meningitis from bile reflux in a lumbar-gallbladder shunt.

OBJECTIVE AND IMPORTANCE: The gallbladder is used to divert cerebrospinal fluid (CSF) in patients with hydrocephalus when all other sites have been exhausted. This is seen in hydrocephalic patients who have reached teenage years but have undergone multiple shunt revisions, abdominal operations and repeated neck vein cannulations during childhood. One complication of the lumbar-gallbladder shunt is discussed as well as its pathophysiologic theory and management. CLINICAL PRESENTATION: A case of a patient with a lumbar-gallbladder shunt who developed chemical meningitis from reflux of bile into the CSF space is presented. The patient presented with generalized seizures. INTERVENTION: Included: ventilatory support, externalization of the shunt, correction of the metabolic abnormalities and administration of anticonvulsants and steroids. CONCLUSION: This case illustrates an unusual occurrence of reflux of bile into the CNS through a lumbar-gallbladder shunt in a patient with long-term complex communicating hydrocephalus. It also demonstrates its mode of presentation and successful management. To our knowledge, this is the first case report of its kind.

Adult↗

PubMed1997

Anterolateral lumbar lipomyelomeningocele: case report and review of the literature.

OBJECTIVE AND IMPORTANCE: Meningoceles associated with defects of the abdominal wall are exceedingly rare. One such complex case is presented along with a review of the relevant literature. The current pathophysiological theories and surgical management are discussed. CLINICAL PRESENTATION: A case of a patient with an anterolateral lumbar lipomyelomeningocele associated with multiple congenital anomalies, including defects in the abdominal wall and urogenital system, is presented. The lipomyelomeningocele presented as an expanding abdominal mass. INTERVENTION: Ventriculoatrial shunting and two operations to repair the myelomeningocele were performed to control the expanding abdominal mass. CONCLUSION: This report illustrates that the surgical management of complex lipomyelomeningoceles is similar to the more common types. It also demonstrates that in the infant in whom the intra-abdominal cerebrospinal fluid collection is the primary cause of the symptoms, cerebrospinal fluid shunting may be used to delay the definitive repair until the dura strengthens, thus avoiding the complications of complex repairs of dura with low tensile strength.

Abdominal Neoplasms↗

PubMed1996

Ependymal/subependymal zone cells of postnatal and adult songbird brain generate both neurons and nonneuronal siblings in vitro and in vivo.

The songbird forebrain continues to generate neurons in adulthood, from precursor cells located in the ependymal /subependymal zone (SZ) over the mediocaudal neostriatum. Precursor mitosis is followed by migration of neuronal daughter cells into the underlying forebrain, along radial fibers derived from the SZ. To define the ontogeny of both the new neurons and their radial guide cells, we employed retroviral insertion of the lacZ gene into neostriatal SZ precursor cells derived from postnatal and adult songbirds. We found that single SZ cells generate both neurons and substrate glia in vitro, and in an analogous fashion, both neurons and radial cells in vivo. This suggests that newly generated neurons and radial cells of the adult avian brain derive from a common pluripotential progenitor.

Animals↗

PubMed1996

Transient coupling of Ng-CAM expression to NgCAM-dependent calcium signaling during migration of new neurons in the adult songbird brain.

The adult avian forebrain continues to generate neurons from subependymal zone (SZ) precursor cells, whose neuronal progeny migrate into the brain upon radial guide fibers. These neurons express the immunoglobulin-family adhesion molecule NgCAM, and their migration in culture is disrupted by anti-NgCAM Fab. Confocal imaging of adult zebra finch SZ loaded with the calcium indicator fluo-3, as well as ratio imaging with the indicator fura-2, revealed that migrating new neurons responded to microgram amounts of NgCAM with reversible increments in cytosolic calcium. The calcium response to NgCAM antigen was developmentally restricted, in that it was only manifested by neurons for roughly the 3- to 4-day period between 6 and 9 DIV, even though NgCAM expression persisted tonically thereafter. The period during which NgCAM elicited a calcium signal corresponded to the postmitotic age at which new, bipolar neurons leave the adult SZ to enter the brain parenchyma in vivo. Accordingly, the calcium response to NgCAM was largely limited to morphologically bipolar cells. Anti-NgCAM IgG also evoked a neuronal calcium signal over the same restricted period that NgCAM protein exerted its effect. These findings suggest a dynamic coupling and uncoupling of calcium-dependent signal transduction pathways to a stably expressed surface adhesion molecule, whose function in a given neuron may therefore evolve with cellular maturation.

Animals↗

PubMed1995

Estrogens and non-estrogenic ovarian influences combine to promote the recruitment and decrease the turnover of new neurons in the adult female canary brain.

The higher vocal center (HVC) of the songbird forebrain exhibits persistent neurogenesis in adulthood, particularly in a region of the mediocaudal neostriatum that is associated with a subventricular layer of estrogen receptive cells. We asked whether estrogens might influence adult neurogenesis, by assessing the effect of ovariectomy on HVC neuronal production in the adult female canary. Fifteen 1-year-old females were separated into groups of ovariectomized, estradiol-replaced ovariectomized, and gonadally intact birds. To label dividing cells and their progeny, the birds were given [3H]thymidine for 8 days, killed 32 days later, and their brains autoradiographed. A significant rise was noted in the number of HVC neurons per section in estradiol-treated birds relative to the untreated control birds. The number of [3H]thymidine-labeled HVC neurons was also higher in the estrogen-treated birds; however, the neuronal labeling index (LI) did not vary as a function of estradiol replacement, as the total number of HVC neurons rose in parallel with the added new neurons. In contrast, the neuronal LI did rise as a result of ovariectomy, and this ovariectomy-associated increase in the LI was not reversed by estradiol. Among non-neuronal cell types, the endothelial LI was higher in estrogen-treated birds than in their untreated counterparts, suggesting estrogen-associated angiogenesis. Radioimmunoassay confirmed that serum estradiol was reduced in the castrated birds. Since estrogen appeared to promote the survival of [3H]thymidine+ neurons, we next sought to determine whether estrogen acted directly on the newly generated neurons, or rather indirectly through an intermediary cell population. To this end, we asked whether the new neurons or their precursors expressed estrogen receptor immunoreactivity (ER-IR). Five adult male canaries were given [3H]thymidine for periods ranging from 2 to 28 days, killed at varying times up to 3 weeks thereafter, then probed for ER-IR and autoradiographed. [3H]thymidine+ cells displayed no detectable ER-IR within their first 4 weeks of postmitotic life. Rather, during migration from the ventricular zone (VZ), the new neurons traversed a layer of mitotically quiescent, ER+ subventricular cells. Double labeling for ER-IR and cell-type selective antigens confirmed that these ER+ cells were neurons. These results indicate that the early survival of new neurons in the adult songbird HVC is promoted by estrogen, and may be mediated by the estrogen-stimulated paracrine release of neurotrophic agents by ER-IR subventricular neurons. Our data suggest that estrogen's promotion of neuronal survival may operate concurrently with an estrogen-independent ovarian suppression of neuronal mitogenesis.

Animals↗

PubMed1995

Hu protein as an early marker of neuronal phenotypic differentiation by subependymal zone cells of the adult songbird forebrain.

The avian forebrain exhibits neurogenesis in adulthood, with neuronal production from ependymal/subependymal zone (SZ) precursor cells. To follow the commitment of newborn cells to neuronal lineage, we used their expression of the Hu family of neuronal RNA-binding proteins to identify them before their migration from the SZ. Adult canaries were injected with [3H]thymidine as a marker of DNA replication, sacrificed after varying intervals, stained for Hu, and autoradiographed. We found that Hu was not expressed by premitotic precursor cells, but rather appeared within hours in their neuronal progeny, which did not embark on parenchymal migration until 4 to 7 days later. Hu was expressed by all neurons, but not glia, both in vivo and in vitro, as determined by ultrastructural analysis as well as co-localization of Hu and cell-type selective antigens. In addition, co-staining for Hu and N-cadherin, whose expression is down-regulated on neuronal emigration from the SZ, revealed their initial co-expression by neuronal daughter cells still within the SZ. These results suggest that Hu expression may be used as a very early indicator of neuronal differentiation by SZ cells. Furthermore, the data indicate that in the adult avian brain, neuronal phenotype is established within hours of precursor mitosis, even though the neuronal daughter cells do not initiate parenchymal migration for at least 4 days thereafter, following their down-regulation of N-cadherin.

Animals↗

PubMed1994

Ruptured mycotic aneurysm presenting as an intraparenchymal hemorrhage and nonadjacent acute subdural hematoma: case report and review of the literature.

The case of a mycotic aneurysm presenting as an intraparenchymal hemorrhage and acute subdural hematoma is described. A 36-year-old man with a history of headaches and fever presented in coma. Brain computed tomography scan revealed a left occipital intraparenchymal hemorrhage and a nonadjacent acute subdural hematoma that was evacuated. Angiography demonstrated an aneurysm on the distal branch of the left posterior cerebral artery consistent with a mycotic aneurysm. This case and a review of the literature are discussed.

Acute Disease↗

PubMed1994

N-cadherin and Ng-CAM/8D9 are involved serially in the migration of newly generated neurons into the adult songbird brain.

In the adult avian forebrain, neurons continue to be produced in the subependymal zone (SZ), from which they migrate upon radial fibers. To identify ligands regulating this process, we studied N-cadherin and Ng-CAM/8D9 expression in HVC, a neurogenic region of the canary neostriatum. N-cadherin was relatively restricted to the SZ and was expressed by dividing, [3H]thymidine-labeled precursor cells. However, cellular N-cadherin was down-regulated prior to neuronal migration from the SZ. Addition of anti-N-cadherin Fab hastened neuronal migration from adult SZ explants, without influencing neuronal number. Unlike N-cadherin, Ng-CAM/8D9 was expressed by migrating neurons. Anti-8D9 Fab inhibited neuronal migration upon cultured ependymoglia, which did not express Ng-CAM/8D9. Thus, the departure of new neurons from the adult SZ may require their suppression of N-cadherin, whereas their subsequent migration and survival may depend upon neuronal expression of Ng-CAM/8D9 and its interaction with a heterophilic radial cell receptor.

Animals↗

PubMedDate not supplied

In vitro neuronal production and differentiation by precursor cells derived from the adult human forebrain.

It has traditionally been held that the adult brain is incapable of significant self-repair, due in part to its inability to generate new neurons. Nevertheless, rodents and birds have been found to harbor neural precursor cells in adulthood. We asked whether the adult human brain might retain such precursors, by culturing samples of temporal lobe under conditions permissive for neuronal differentiation, while exposed to 3H-thymidine. Adult human temporal lobe cultures, derived from cortex, subcortex, and periventricular subependymal zone (SZ), were incubated for 7-28 d, stained for neuronal and glial antigens, and autoradiographed. Neuron-like cells were found in explant outgrowths and monolayer dissociates of SZ and periventricular white matter, but not cortex; they expressed neuronal antigens including MAP-2, MAP-5, NF, and N-CAM, and were GFAP-. Neurons responded to K+ depolarization with rapid and reversible increases in intracellular Ca2+, with much greater increments than those noted in glia. Although most neurons were not 3H-thymidine labeled, a small number of MAP-2+ and MAP-5+/GFAP- cells did incorporate 3H-thymidine, suggesting neuronal production from precursor mitosis. Rare 3H-thymidine+ neurons were also found in cultures of subventricular white matter; in these, GFAP+ astrocytic mitogenesis was common, while O4+ oligodendrocytes, although the predominant cell type, were largely postmitotic. Thus, the adult human forebrain harbors precursor cells that retain the potential for neuronal production and differentiation in vitro.

Adolescent↗