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Biomedical subjects

K Elisevich

Publications and source records attributed to K Elisevich.

At least 37 records · Page 2Linked to original sources
PubMed1994

Vascularization and microvascular permeability in solid versus cell-suspension embryonic neural grafts.

Vascularization and microvascular permeability were assessed in a comparative study of solid (organized) and cell-suspension (dissociated) fetal nigral grafts implanted in the dopamine-deprived striatum of adult rats. Both graft types were analyzed by chromogen detection of intravenously injected horseradish peroxidase (HRP), which outlined vessel walls, and, in cases in which the blood-brain barrier was compromised, permeated the graft and host parenchyma. Survival of graft-derived dopaminergic cells was assessed using tyrosine hydroxylase (TH) immunocytochemistry. Glial reactivity to cell-suspension grafts was similarly assessed with an antibody directed against glial fibrillary acidic protein. Morphometry revealed significantly higher microvessel density in the cell-suspension grafts (p < 0.001), which effectively equaled that found in the contralateral striatum despite rather prominent surrounding glial reactivity. Capillaries in the cell-suspension grafts were not permeable to blood-borne HRP at postimplantation study times of 7, 14, and 30 days whereas, in the solid grafts, permeability in some cases could be detected for up to 30 days. Large numbers of cells immunoreactive for TH were seen in cell-suspension grafts; in contrast, few if any were found in the majority of solid transplants. The multiple-fragment solid graft implant model used clinically compares poorly with the cell-suspension model because it lacks consistency in early revascularization and shows a greater (albeit temporary) tendency for blood-brain barrier dysfunction. Delayed and inadequate vascularization of the solid graft is likely to account for graft failure more often than in the cell-suspension graft. Similarly, a certain critical number of specific grafted cells are required to achieve sufficient expression to bring about a favorable response in the disabled host, and this expression appears to be achieved less consistently with the solid implant technique.

Animals↗
PubMed1993

GABAergic synaptic interactions in the substantia nigra.

The substantia nigra receives a strong GABAergic input from the ipsilateral striatum and globus pallidus. Nigral GABAergic synaptic interactions have been described in the pars compacta (SNC) and pars reticulata (SNR) but not in the pars lateralis (SNL). The SNR and particularly the SNL are the nodal points of the GABAergic nigrotectal pathway. The present study analyzes the synaptic connections of GABAergic and dopaminergic neurons in each of the divisions of the substantia nigra by employing a double-labeling immunocytochemical technique at the light and electron microscope levels. Glutamic acid decarboxylase (GAD)-containing terminals make symmetrical synaptic contacts with dopaminergic neurons in the SNC and SNR. Neurons that contain GAD also receive a GABAergic input in the SNR and SNL. The proportion of GAD-GAD contacts appears to be highest in the SNL where virtually all GAD-positive terminals are found to be in synaptic contact with or apposed to GAD positive profiles. This study demonstrates a strong GABAergic input onto nigral dopaminergic neurons and GABAergic neurons in the SNR and SNL. This GABAergic influence which is ostensibly striatal or pallidal in origin is particularly prominent in relation to the SNL-mediated nigro-collicular pathway.

Animals↗
PubMed1993

Compartmental origin of the striato-entopeduncular projection in the rat.

The mammalian neostriatum is divisible into neurochemically and cytoarchitectonically distinct striosome and matrix compartments. This compartmentalization is respected by many afferent and efferent projections of the striatum. The distribution of distinct types of neuroactive substances and receptors and the unique connections of the striosome and matrix suggest a functional segregation between these compartments. The present study examines the organization of efferent projections from each of the striatal compartments to the entopeduncular nucleus (EPN), a major output center of the basal ganglia. The fluorescent retrograde tracer fluorogold, or rhodamine-conjugated dextran, was injected into the lateral habenula or the ventrolateral nucleus of the thalamus of adult Wistar rats to identify the topographical organization of EPN-habenular and EPN-thalamic neurons. Fluorogold was then placed into the rostral or caudal parts of the EPN, identified from the previous experiment as areas containing predominantly EPN-habenular or EPN-thalamic neurons, respectively. Sections containing retrogradely labeled neurons in the neostriatum were simultaneously immunolabeled for calbindin-D28kDa, a calcium-binding protein found exclusively in the projection neurons of the matrix. The results indicate that the striatal projection to the EPN-habenular and EPN-thalamic parts of the EPN originates from striosome and matrix neurons, respectively. The duality of striatal outflow involving the EPN suggests a mechanism whereby the striosome is integrated into subcortical pathways that modulate the activity of the basal ganglia via the ascending serotoninergic projection from the dorsal raphe nucleus, whereas the matrix is involved in a loop that includes the thalamus and the cerebral cortex.

Animals↗
PubMed1993

Biotinylated dextran: a versatile anterograde and retrograde neuronal tracer.

A powerful and versatile axonal tracing method using biotinylated dextran, a novel analogue of biotin, is described. Pressure injection of varying volumes of 5% biotinylated dextran into various parts of the brain and spinal cord resulted in Golgi-like retrograde labeling and PHA-L-like anterograde labeling. The tracer filled the finest processes, revealing terminal axonal ramifications, distal dendrites and dendritic spines and excrescences. Extensive anterograde and retrograde labeling occurred in all pathways studied and in animals of all ages. Labeling appeared as early as 48 h and remained unchanged up to 14 days following injection. Biotinylated dextran can be detected easily with any avidin-conjugated marker for light and electron microscopic study. The resultant labeling can be combined readily with other morphological methods, such as tract tracing and/or immunocytochemical demonstration of endogenous substances. Biotinylated dextran is thus an efficient anterograde and retrograde tracer that can be combined with other neuroanatomical techniques to study details of synaptic interaction at all levels of dendritic organization.

Animals↗
PubMed1993

Normalization of striatal proenkephalin and preprotachykinin mRNA expression by fetal substantia nigra grafts.

The expression of striatal proenkephalin and preprotachykinin mRNA was studied in Wistar rats following unilateral injections of 6-hydroxydopamine into the nigrostriatal pathway and after grafting dopaminergic fetal cell suspensions into the dopamine-depleted striatum. Striatal dopaminergic deafferentation resulted in an amphetamine-induced rotational asymmetry, an increase in ipsilateral striatal proenkephalin mRNA, and a decrease in preprotachykinin mRNA expression. Twelve months following grafting, proenkephalin and preprotachykinin mRNA returned to near-normal levels in contrast to control nongrafted lesioned animals. In addition, reversal of the rotational asymmetry was routinely observed. This study has demonstrated long-term graft-induced functional recovery coincident with normalization of striatal proenkephalin and preprotachykinin mRNA expression.

Animals↗
PubMed1992

In vivo growth of C6 glioma cells transfected with connexin43 cDNA.

In order to examine the possible role of intercellular communication via gap junctions in the control of tumor growth, we have transfected C6 glioma cells with connexin43 cDNA. We obtained several clones with variable expression of connexin43. The growth rate of these clones in culture was inversely related to the degree of expression of the transfected cDNA. To examine the growth of these transfected cells in vivo, cells were grown in spinner culture flasks to form spheroids 250-300 microns in diameter. Spheroids of nontransfected C6 cells produced large gliomas. Immunohistochemical and in situ hybridization analyses revealed relatively high levels of connexin43 protein and mRNA in the host tissue, while little of this protein was detected in the glioma. In contrast, spheroids of connexin43-transfected cells grew more slowly and exhibited elevated levels of connexin43 protein and mRNA. These findings suggest that the expression of connexin43 may be associated with the control of brain tumor growth in vivo.

Animals↗
PubMed1992

Substance P synaptic interactions with GABAergic and dopaminergic neurons in rat substantia nigra: an ultrastructural double-labeling immunocytochemical study.

The distribution of substance P (SP), tyrosine hydroxylase (TH), and glutamic acid decarboxylase (GAD) immunoreactivity in the substantia nigra of the rat was studied by means of an ultrastructural double-labeling immunocytochemical method. Direct synaptic contact between SP-immunoreactive terminals and GAD-positive nigral neurons was more often observed in the pars lateralis than the pars reticularis and was rarely observed in the pars compacta. Substance P-positive terminals also formed synapses with cell bodies and dendrites of TH-positive, dopaminergic neurons in the pars compacta and pars reticulata. Multiple SP-immunoreactive terminals were often observed with symmetrical and, less frequently, asymmetrical synapses on individual TH-containing dendrites. Evidence of SP-containing terminals contacting both GABAergic and dopaminergic neurons in the substantia nigra suggests a direct excitatory action upon nigral projection neurons.

Animals↗
PubMed1991

Dopaminergic innervation of substance P-containing striatal neurons by fetal nigral grafts: an ultrastructural double-labeling immunocytochemical study.

Evidence for survival and growth of fetal substantia nigra grafts in host striatum and partial reversal of behavioural and biochemical deficits in the host animal is well documented. Afferent synaptic connections arising from the graft and contacting host structures have also been reported; however, the properties of the neurons receiving this input is less clear. The purpose of this study was to determine if substance P-containing neostriatal neurons receive a dopaminergic input from nigral grafts. Fetal substantia nigra cell suspensions were stereotaxically implanted in the deafferented neostriatum of Wistar rats 2 weeks after a unilateral 6-hydroxydopamine (6-OHDA) lesion in the ipsilateral substantia nigra or medial forebrain bundle. The ultrastructural features of the graft-host synaptic interactions were analysed by employing an electron microscope immunocytochemical double-labeling technique. Tyrosine hydroxylase (TH) and substance P-immunoreactive structures were simultaneously demonstrated by means of the peroxidase-antiperoxidase method using two different chromogens with distinct reaction products easily differentiated at the light and electron microscope levels. TH-immunoreactive sites were first demonstrated using 3,3'-diaminobenzidine tetrahydrochloride (DAB); then substance P immunoreactivity was localized using benzidine dihydrochloride (BDHC). TH-immunoreactive terminals of axons originating from the graft made synaptic contacts with substance P-positive cell bodies and dendrites from the host. These results indicate that at least partial restoration of the normal nigrostriatal circuitry can be achieved following nigral grafts. The demonstration of specific synaptic input on host substance P neurons provides an anatomical basis for direct functional modulation of the deafferented host neostriatum by the nigral graft.

Animals↗
PubMed1991

Effects of injection mechanics, pH of infusate and 6-hydroxydopamine on cerebromicrovascular permeability in rats.

The effects of altering the rate, manner and vehicle used for intracerebral injection upon microvascular permeability were studied in Sprague-Dawley rats employing horseradish peroxidase histochemistry. The volume of vehicle delivered and the site of intracerebral injection were kept constant. In comparison to continuous infusion, vascular permeability was significantly greater following manual (intermittent) injections; however, no differences were found when the infusion rate was decreased 10-fold. Use of a buffered vehicle (Hanks' balanced salt solution) with pH adjusted to 7.4, in contrast to the more commonly used non-buffered vehicle (saline-ascorbate), resulted in significant reductions in permeability. The apparent influence of the agent 6-hydroxydopamine (6-OHDA) on changes in vascular permeability was found to vary depending on the type and pH of the vehicle used for injection. Significantly greater permeability resulted with saline-ascorbate (pH 3.1) as the vehicle when compared to Hanks' balanced salt solution (pH 7.4). Changes in vascular permeability can therefore be produced by varying mechanical and vehicular factors which, in the case of 6-OHDA, far outweigh previously reported permeability changes specifically attributed to this neurotoxin.

Animals↗
PubMed1991

En block forehead reconstruction with split-thickness cranial bone.

This report demonstrates the utility of split-thickness cranial grafts harvested by craniotomy in the reconstruction of the entire forehead in an en bloc fashion. The technique allows a cosmetic recontouring of large surfaces of the cranial vault in particular, with little or no need for multiple extracranial grafts. Computer imaging and three-dimensional graphic reconstruction lend themselves well to preoperative planning.

Adult↗
PubMed1991

The fastigial pressor response. Case report.

A distinct vasomotor and cardioregulatory response first identified experimentally was elicited intraoperatively in a 6-year-old girl by local mechanical stimulation in the vicinity of the fastigial nucleus of the cerebellum. These findings are discussed in the light of current experimental knowledge of the anatomy and physiology of the fastigial pressor response.

Astrocytoma↗
PubMed1991

Orbital rim and malar advancement for unilateral coronal synostosis in the older pediatric age group.

The authors describe a technique for lateral orbital rim and malar advancement in patients in the older pediatric age group. The technique makes use of a strip craniotomy containing the supraorbital margin, greater sphenoid wing, and temporal bone, with en bloc inclusion of the lateral orbital rim, zygoma, and malar prominence. The method allows a contoured yet stable construction secured in a tongue-in-groove fashion with plate-and-screw fixation. It creates a symmetrical reconstruction of both frontal and lateral orbital aspects in the untreated or inadequately treated older plagiocephalic child with orbital dystopia. The accompanying malar recession is likewise corrected.

Adolescent↗
PubMed1991

Microorbitalism: a technique for orbital rim expansion.

A simple technique for orbital aperture expansion to facilitate placement of ocular prostheses is described. Both superolateral and inferolateral orbital margins are released by means of a single burr hole craniectomy of the frontosphenoid bone behind the orbital process of the frontal bone. Vertical and horizontal marginal lengthenings are performed by a rotatory displacement of one bone segment alongside the other. The expanded osseous aperture is secured with wire and plate-and-screw fixation following a supraorbital rim craniectomy to allow an adequate fit. The result provides for easier access of ocular prostheses and tissue expanders. The method has been applied to a series of patients with microorbitalism due to unilateral or bilateral congenital anophthalmia over the past 3 years without complication and with excellent results. Three-dimensional re-formatted CT reconstructions of the craniofacial skeleton are shown preoperatively and postoperatively.

Child, Preschool↗
PubMed1990

Fourth ventricular schwannoma. Case report.

A schwannoma arising from the dorsum of the pontomedullary junction and presenting as an exophytic mass in the fourth ventricle is described. A ventricular schwannoma has not previously been reported in the literature. The presenting clinical and radiographic features and the pathology of this tumor are summarized, and an explanation is sought for its unusual location.

Brain Neoplasms↗
PubMed1988

Vestibular nucleus inputs to paramedian reticulospinal neurons in the cat.

Experiments were done in chloralose-anesthetized cats to identify single units in the paramedian reticular nucleus (PRN) that responded to stimulation of pressor sites in the vestibular nucleus complex (VNC) and that projected directly to the intermediate gray (IG) region of the upper thoracic cord. Forty-seven units responded orthodromically to stimulation of the ipsilateral VNC with a mean latency of 6.3 +/- 0.6 ms: 44 were excited and 3 were inhibited. Of these 47 units, 29 (62%) also were antidromically activated by stimulation of the ipsilateral IG at the level of T2. These data provide electrophysiological evidence for the existence of neurons in PRN that receive VNC inputs and project directly to spinal autonomic areas, and suggest that this pathway may be involved in mediating vestibulosympathetic reflex responses associated with postural adjustments.

Action Potentials↗
PubMed1988

Cardiovascular afferent and fastigial nucleus inputs to paramedian reticulospinal neurons.

In chloralose anesthetized, paralyzed and artificially ventilated cats, the region of the paramedian reticular nucleus (PRN) was systematically explored for single units antidromically activated by electrical stimulation of histologically verified sites in the intermediate gray region of the upper thoracic cord (T2). These antidromically identified units were then tested for their orthodromic responses to electrical stimulation of ipsilateral carotid sinus nerve (CSN) and of pressor sites in the contralateral fastigial nucleus (FN). Sixty-two histologically verified single units, located predominantly in the caudal half of the ventral PRN, were antidromically activated with latencies corresponding to a mean conduction velocity of 36.4 +/- 2.1 m/s. Of these units 25 (40%) were excited orthodromically by stimulation of the CSN and/or FN: 5 to stimulation of the CSN only (mean latency, 18.3 +/- 9.9 ms), 6 to stimulation of the FN only (mean latency, 7 +/- 1.7 ms), and 14 to stimulation of both the CSN and FN (mean latencies, 12.3 +/- 2.9 ms and 8.4 +/- 1 ms, respectively). These data provide electrophysiological evidence for the existence of PRN reticulo-spinal neurons that integrate and relay cardiovascular afferent information from the CSN and FN to spinal autonomic neurons.

Action Potentials↗
PubMed1987

Collateral branching in axonal projections to spinal cord from paramedian reticular nucleus neurons.

Experiments were done in cats to identify neurons in the paramedian reticular nucleus (PRN) sending collateral axons to the region of the intermediolateral nucleus (IML) at different levels of the thoracic cord by using lectin-conjugated horseradish peroxidase (HRP) and double-labeling fluorochrome histochemistry to retrogradely label PRN neurons. Injections of Fast blue (FB) into the spinal cord at the T2 level centered in the region of the IML were coupled with injections of Nuclear yellow (NY) into the ipsilateral cord at either the T4 or T7 levels centered in the region of the IML. Neurons in the PRN retrogradely labeled after diffusion of HRP into the region of the IML at the T2 level were observed throughout the rostrocaudal extent of the ventral PRN. In addition, a few labeled neurons were noted in the ventral portion of the dorsal PRN. About 40% of the neurons in the PRN which were labeled with FB after an injection at the T2 level were also labeled with NY injected into the cord in further caudal segments. These data suggest that the PRN may exert its influence on the cardiovascular system partly through collateral axonal branches to widely separated populations of sympathetic preganglionic neurons in different spinal segmental levels.

Amidines↗