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J T Hansen

Publications and source records attributed to J T Hansen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Adrenal chromaffin cells as transplants in animal models of Parkinson's disease.

The field of neural transplantation has moved rapidly forward in the last decade. Initially, fetal cells were used as implants to investigate their potential to ameliorate deficits in animal models of Parkinson's disease. However, because of the moral and legal problems associated with the use of fetal tissues in humans, alternative sources of donor tissue were sought which possessed the structural and functional characteristics needed to improve motor function in Parkinsonian patients. To date, one of the most promising tissues being investigated is the adrenal medulla, whose chromaffin cells possess an inherent plasticity of form and function. Transplanted chromaffin cells currently are being studied by a variety of approaches, including electron microscopy, in mouse, rat, and primate models of Parkinson's disease. An overview of the role of the chromaffin cell in this exciting and clinically important arena is briefly reviewed, with an emphasis on the fine structure of implanted chromaffin cells.

Adrenal Medulla↗
PubMed1989

Rodent and primate adrenal medullary cells in vitro: phenotypic plasticity in response to coculture with C6 glioma cells or NGF.

In order to maintain a chronic supply of growth factor for medulla cells in vitro, chromaffin cells from rat, African green monkeys and man were co-cultured with C6 glioma cells, which secrete growth factors that sustain sympathetic neurons in vitro. The response of chromaffin cells to coculture was compared to treatment of medullary cells with nerve growth factor (NGF) alone. Dispersed chromaffin cell preparations were obtained by a trypsin-collagenase procedure, and subjected to differential plating on collagen-coated surfaces. With both human and monkey tissue, non-chromaffin cells did attach to the culture plates and an enriched chromaffin cell population could be replated. Rat adrenal medulla cells survived very poorly in vitro and were not enriched in this procedure. Cultured human and monkey chromaffin cells survived as epithelial cells (50%) and showed neuritic outgrowth on 55 to 66% of the cells after eight days when treated with nerve growth factor (NGF). These cells showed strong catecholamine histofluorescence, tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DBH) immunoreactivity. In contrast, only ten percent of adult rat chromaffin cells survived in culture, although NGF treatment rescued an additional 20% of the cells and induced neuritic outgrowth after one week in vitro. C6 glioma cells were treated with mitomycin C bromodeoxyuridine to inhibit mitosis and were plated with the various medulla cells in a one to one ratio. Both human and monkey chromaffin cells expressed extensive and enhanced neuritic arborization within eight days of co-culture, (64-82% respectively) and exhibited intimate contact with the glioma cells as seen at the ultrastructural level. Importantly, survival of adult rat adrenal medulla cells was enhanced to 50% or more with 40% of the cells extending neurites when co-cultured with glioma cells for seven days. Chromaffin cells from all three species reacted for TH, DBH and PNMT in co-culture and were histo-fluorescent. The majority of these cells were also immunoreactive for serotonin and enkephalin, while only 37% of chromaffin cells indicated the presence of NPY. These data indicate that adrenal medulla can be maintained in vitro as the neuronal phenotype when co-cultured with growth factor producing cells and that this strategy may be useful for in vivo transplantation studies.

Adrenal Medulla↗
PubMed1988

Organization, fine structure, and viability of the human adrenal medulla: considerations for neural transplantation.

Recent reports of adrenal medullary autografts in patients with Parkinson's disease raise several important questions with respect to the cell types actually being transplanted as well as the potential for chromaffin cell banking prior to neural transplantation. In this study, we determined the general morphological characteristics of the human adrenal medulla and assessed factors important for the maintenance of cultured chromaffin cells for later use as transplants. The human adrenal medulla contained islands of cortical cells scattered throughout the gland as well as Schwann cells, nerve endings, endothelial cells, pericytes, isolated ganglionic neurons, and connective tissue elements such as fibroblasts and smooth muscle cells. Because many of these cell types are mitotically active, transplantation of medullary fragments that contain these cells could have far-reaching consequences. One approach that could circumvent the problems arising from multiple cell types in the medulla is differential plating of chromaffin cells prior to transplantation. Differential plating yielded relatively pure populations of chromaffin cells that demonstrated excellent viability if processed within 2 hours after cessation of the gland's circulation. Chromaffin cells cultured in the presence of nerve growth factor exhibited a neuronal phenotype, possessed catecholamine histofluorescence, and displayed tyrosine hydroxylase- and dopamine beta-hydroxylase-like immunoreactivity. The sex and age of the donor did not affect cell viability or morphological characteristics.

Adrenal Medulla↗
PubMed1988

Adrenal medullary autografts into the basal ganglia of Cebus monkeys: graft viability and fine structure.

Based largely upon studies done in rats, a number of medical centers are now performing autografts of adrenal medullary tissue in consenting patients with Parkinson's disease. However, a systematic experimental evaluation of adrenal medullary autografts in nonhuman primates is necessary. This study provides a detailed analysis of the implant site at the fine structural level 30 days post-transplantation in the Cebus monkey. Five normal and two 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP)-treated Cebus monkeys received adrenal medullary autografts using an open microsurgical approach (n = 3) or via stereotactic placement with a tissue carrier (n = 4). Analysis of preimplant samples of the adrenal medulla confirmed that viable chromaffin cells were implanted into the basal ganglia. However, 30 days later, the implant site resembled a chronic inflammatory focus, with grafted chromaffin cells identified ultrastructurally in only two of the seven transplanted monkeys. The grafted cells showed overt signs of cellular degeneration and were surrounded by phagocytic macrophages. All of the implant sites, regardless of the surgical approach, were filled with macrophages, cells of hematogenous origin, and fibrous astrocytes. The vasculature of the implant site was of the nonfenestrated type, characteristic of the host striatum. Despite the poor survival of implanted chromaffin cells, robust sprouting of tyrosine hydroxylase-like immunoreactive fibers was evident in the striatum adjacent to the implant site (see accompanying manuscript, M.S. Fiandaca, J. H. Kordower, J.T. Hansen, S.-S. Jiao, and D.M. Gash, 1988, Exp. Neurol. 102: 76-91), suggesting that implantation may have precipitated a host response that was beneficial to the transplanted animal. Additional studies that provide a better understanding of the cellular elements residing in the implant site and their potential for trophic influence seem warranted.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1988

Adrenal medullary autografts into the basal ganglia of Cebus monkeys: injury-induced regeneration.

Questions arising from recent clinical neural transplantation trials in Parkinson's disease have under-scored the necessity for a thorough experimental evaluation of the structural and functional consequences of this procedure. The present study investigated the neuroanatomical host reaction to intrastriatal implants in normal and 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP)-treated nonhuman primates. Nine monkeys (Cebus apella) received intrastriatal implants using either a stereotactic approach with a silver tissue carrier or an open microsurgical procedure. Seven of these animals received intrastriatal adrenal medullary autografts, while two received control implants consisting of the tissue carrier alone. One month following transplantation, the hosts' brains were evaluated via immunohistochemical and routine histologic methods. In both MPTP-treated and normal monkeys, enhanced ipsilateral expression of tyrosine hydroxylase-like immunoreactive (TH-IR) fibers in the caudate nucleus was observed, despite minimal survival of adrenal chromaffin cells in the implants. The intensity of this response was greatest adjacent to the implant site, but a clearly increased degree of ipsilateral striatal fiber staining also could be seen several millimeters from the graft. TH-IR fibers also were more dense and of thicker caliber throughout the nigrostriatal and mesolimbic pathways ipsilateral to the implant. Control stereotactic implants, consisting of a silver tissue carrier alone, produced a similar enhancement of immunoreactive fibers, suggesting an induction of TH-IR fibers by the parenchymal injury produced during surgical implantation. There are two major hypotheses proposed to explain why adrenal medullary grafts may promote functional recovery in human parkinsonism: (1) replacement of lost striatal neurotransmitter (dopamine) by the viable grafted tissue, or (2) induction of recovery of remaining host dopaminergic systems by the implantation procedure. Our current data appear to support the latter.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1988

Comparison of adrenal medullary, carotid body and PC12 cell grafts in 6-OHDA lesioned rats.

The survival and functional properties of dispersed cell implants of catecholaminergic cells obtained from the peripheral nervous system of adult rats (adrenal medulla and carotid body glomus cells) and PC12 cells from a rat pheochromocytoma cell line were examined following transplantation into the striatum of the adult rat. The host animals, all with unilateral 6-hydroxydopamine (6-OHDA) nigrostriatal lesions, were divided into 5 groups: (1) PC12 cells transplanted into Cyclosporin-A treated hosts; (2) PC12 cell grafts into hosts without Cyclosporin-A treatment; (3) grafts of adrenal medullary cells; (4) grafts of glomus cells; and (5) vehicle controls. All animals were sacrificed one month after transplantation. Immunocytochemical staining for tyrosine hydroxylase, the rate-limiting enzyme for catecholamine synthesis, was used to identify and characterize the grafted cells. PC12 cells were detected in four of six Cyclosporin-A treated rats, and two of these grafts developed into tumors. However, only one of the six non-Cyclosporin-A treated hosts was found to have surviving PC12 cells, and none of these rats developed tumors. No significant differences in rotational behavior were seen in either of the PC12 cell recipient groups. Grafted cells could be identified in all of the adrenal medullary and glomus cell recipients. However, the number of surviving cells was quite limited, with not more than 100 tyrosine hydroxylase-positive grafted cells found in any one recipient. Tyrosine hydroxylase-positive fibers were present adjacent to the transplants in these latter graft recipients, but the fibers appeared to be of host origin rather than from the grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1987

Effects of salt loading on the fractional volume of atria-specific granules in Dahl salt-sensitive and salt-resistant rats.

The cardiac atria are known to play a role in blood volume homeostasis, secreting a peptide that induces a potent natriuresis and diuresis. This peptide is atrial natriuretic factor (ANF), and its primary site of storage is within atria-specific granules found in atrial cardiocytes. Since salt loading results in an increase in circulating levels of ANF, our aim was to determine if the atria-specific granule population in the cardiocytes of Dahl rats would decrease accordingly. To this end, the fractional volume of the atria-specific granules was determined by ultrastructural morphometric analysis in the Dahl salt model of hypertension. This analysis was performed on the right atria of Dahl Salt-resistant (DR) and salt-sensitive (DS) rats fed either a low-salt (0.4%) or high-salt (8%) diet for 12 weeks prior to sacrifice. DR and DS rats fed a low-salt diet had significantly reduced plasma sodium levels and osmolalities, and a significantly lower mean arterial blood pressure than did rats fed a high-salt diet. The fractional volume of atria-specific granules was significantly lower in salt-loaded DR (P less than 0.01) and DS (P less than 0.025) rats than in their respective low-salt controls. This significant decrease in atrial granules corresponds to the reported decrease in the storage of atrial ANF in salt-loaded rats, and provides a morphological verification of the biochemical studies. Moreover, these results, in combination with a growing body of physiological data, lend support to the hypothesized role of ANF in the regulation of water-electrolyte balance, which may play an important role in cardiovascular pathophysiological states related to hypertension.

Animals↗
PubMed1987

Morphology of the carotid sinus wall in normotensive and spontaneously hypertensive rats.

The morphology of the carotid sinus region of the internal carotid artery was studied in spontaneously hypertensive rats (SHR) at 5, 8, 16, and 24 weeks of age. The carotid sinus region occupied the proximal millimeter of the internal carotid artery, and was easily recognizable by the presence of an extensive adventitial capillary plexus, which was absent on adjacent arteries (e.g., common and external carotid arteries). Methylene blue-stained whole-mount preparations showed the extent of baroreceptor nerves over the sinus. Baroreceptor fibers terminated in distinctive bulbous-like endings, which, at the ultrastructural level, were filled with mitochondria. No differences were noted in the sinus adventitial capillary network or baroreceptor distribution between SHR and age-matched Wistar-Kyoto (WKY) normotensive control animals. With the onset of a significant rise in SHR blood pressure, the carotid sinus wall increased in thickness and total vessel size. The wall/lumen ratios were significantly larger in the SHR than in age-matched WKY ratios in all age groups. SHR carotid sinus vessel enlargement was uniform throughout the vessel tunics, with no significant change in the proportion of the tunica media occupied by smooth muscle cells. The increase in the carotid sinus wall thickness associated with increasing hypertension could affect the ability of the sinus to distend and may play a secondary role in the maintenance of hypertension by compromising baroreceptor nerve ending sensitivity.

Animals↗
PubMed1987

Evidence that dopamine regulates norepinephrine synthesis in the rat superior cervical ganglion during hypoxic stress.

Electrical stimulation of preganglionic nerves is known to increase norepinephrine synthesis in the rat superior cervical ganglion in vitro, an effect which appears to be partially regulated by a non-cholinergic transmitter. In the present study, we sought to determine whether sympathetic stimulation also increases norepinephrine synthesis in the rat ganglion in vivo, and whether dopamine released from ganglionic interneurons might regulate this response. To tackle these questions, rats were pretreated with spiroperidol, a selective dopamine-receptor blocker, and then were sympathetically stimulated by exposure to severe hypoxic stress. Other rats were pretreated with vehicle alone before the hypoxic exposure. Norepinephrine synthesis in ganglia was assessed by measuring endogenous tyrosine hydroxylase activity and norepinephrine turnover. We found that hypoxic stress increased both of these indices of norepinephrine synthesis, but only in rats pretreated with spiroperidol. No such response was detected in rats pretreated with vehicle. These results indicate that sympathetic stimulation increases norepinephrine synthesis in the rat superior cervical ganglion in vivo, and that dopamine released from interneurons might regulate this response.

Animals↗
PubMed1986

Immunocytochemical staining of Histoplasma capsulatum at the electron microscopic level.

Rabbits were immunized with histoplasmin emulsified in Freund's complete adjuvant. Antibody raised in these rabbits was exposed to Histoplasma capsulatum yeast cells, either in tissue culture medium, or after in vitro or in vivo phagocytosis by mouse macrophages. The sites of antibody binding were identified using an immunoperoxidase technique. At least two sites of antibody binding were identified, one to the fungal cell wall and the other to the outer cell membrane. Within 6 h after phagocytosis by macrophages, fungal cell walls appeared roughened, with what appeared to be cell wall antigen released into the phagolysosome, appearing associated with the phagolysosome membrane, and possibly adjacent macrophage cytoplasm. Similar staining of fungal antigen was noted in alveolar macrophages which had ingested Histoplasma capsulatum after a respiratory challenge. This method may be useful in detailing the host/pathogen interactions which occur in human pulmonary histoplasmosis.

Animals↗
PubMed1986

Elemental concentration gradients between subcellular compartments.

To gain information on the mechanisms involved in the establishment and maintenance of subcellular gradients of Na, K, Cl and other elements in the flagellate, Euglena gracilis, we turned to the technique of ultracentrifugal stratification of its intracellular contents, which is achieved without loss of viability or cell rupture. Stratified and non-stratified Euglena were cryofixed for energy-dispersive X-ray microanalysis of Na, K, Cl and other elements in thin freeze-dried cryosections. A number of significant elemental concentration differences (expressed as mmol kg-1 dry weight) were found between chloroplast, nucleus, paramylon granules and open cytoplasm (which contained ribosomes, membranes and macromolecules associated with the cytomatrix) in the non-stratified cells. Stratification caused several ions to be redistributed. For example, we observed a significant increase in K and Cl in the nucleus, which was correlated with the condensation of chromatin. Also Cl, but not Na, decreased significantly in the region of cytoplasm that was cleared of observable ribosomes, membranes and macromolecules associated with the cytomatrix, as well as of observable cytochemical enzyme activity. We conclude from the data that more than half of the Cl in open cytoplasm was adsorbed to or entrapped in material that was removed by ultracentrifugation. Thus, it appears that a close association of at least one ion, Cl, with ultracentrifugable material is involved in maintenance of the measured Cl concentration in the open cytoplasm of the non-stratified cell.

Animals↗
PubMed1986

Substance P-like immunoreactivity in rat and cat carotid bodies: light and electron microscopic studies.

Substance P-immunoreactive (SP-1) structures in the carotid bodies of rats and cats were examined with the light and electron microscopes. In both species SP-I varicose nerve fibers were located singly in the interstitial connective tissue in close association with blood vessels. They were small unmyelinated fibers enveloped in a common Schwann cell sheath with other SP-negative fibers. Some of SP-I fibers contained large dense-cored granules and small clear vesicles in addition to microtubules and mitochondria and probably represented nerve fiber varicosities. The latter often were found incompletely invested by Schwann cell sheaths. SP-fibers were found occasionally in the envelopes of supporting cells at the periphery of parenchymal cell groups. However, none of the nerve terminals making synaptic contacts with glomus cells exhibited SP-like immunoreactivity. In cat carotid bodies some glomus cells showed moderate to intense SP-like immunoreactivity. The intense SP-I glomus cells displayed numerous dense-cored vesicles of 85 to 140 nm in diameter and frequently showed synaptic contacts with SP-negative nerve terminals. In rat carotid bodies we were unable to detect consistent SP-immunoreactivity in glomus cells. Our results do not favor the hypothesis that SP is a neurotransmitter/modulator in the chemoreceptor afferents synapsing on glomus cells in either the cat or rat carotid body. However our results support the hypothesis that SP in cat glomus cells may play a role in the modulation of chemoreceptor activity.

Animals↗
PubMed1985

Ultrastructure of the primate carotid body: a morphometric study of the glomus cells and nerve endings in the monkey (Macaca fascicularis).

The carotid body of the monkey (Macaca fascicularis) was studied at both the light and electron microscopic levels in an effort to provide a detailed quantitative characterization of this chemoreceptor organ in the primate. Structurally, the monkey carotid body was organized into lobules of from three to eight glomus cells (in section) and their ensheathing supporting cells. Interspersed among the lobules was abundant connective tissue stroma, fibroblasts and mast cells. Fenestrated capillaries, small arterioles and venules also permeated the organ. Each supporting cell partially ensheathed about three glomus cells and could be easily differentiated from glomus cells by their darker cytoplasmic staining, lack of dense-core vesicles and angular nuclear profile. Glomus cells exhibited an intense catecholamine histofluorescence and contained abundant dense-core vesicles. On the basis of dense-core vesicle size, shape and numerical density, four types of glomus cells were identified. The most common type (62% of all glomus cells) contained vesicles with an average diameter of 219 nm and a density of 8 vesicles per micron 2 of cytoplasm. The second type possessed larger vesicles (264 nm in diameter) and accounted for about 14% of all glomus cells. A third type of glomus cell contained smaller (167 nm) and fewer (5 vesicles per micron2) dense-core vesicles. The fourth type of glomus cell contained pleomorphic-shaped vesicles with a maximal diameter of 232 nm. Each of these last two types accounted for about 12% of all glomus cells. All four types of glomus cells were innervated, averaging 1.43 nerve endings per glomus cell (in sections). Nerve endings were primarily of the bouton-like variety averaging 2 micron2 in sectional area and containing 34.3 clear-core synaptic vesicles (average size 73.5 nm in diameter) per micron2 of cytoplasm. Of the 57 nerve endings examined in single sections, 16% displayed junctions typical of synaptic specializations and most of these were presynaptic to glomus cells. Glomus cell-glomus cell synapses were not observed. Based on these quantitative observations and on previous studies of carotid body cytoarchitecture in other laboratory species, it appears that the primate organ most closely resembles the cat carotid body, although several differences exist.

Animals↗
PubMed1985

Dopamine beta-hydroxylase-like immunoreactivity in the rat and cat carotid body: a light and electron microscopic study.

Immunocytochemical localization of dopamine beta-hydroxylase (DBH) was used to study the synthesis and storage sites of norepinephrine (noradrenaline) in the rat and cat carotid bodies. In the rat carotid body some parenchymal cells exhibited strong DBH-like immunoreactivity (DBH-I), while others displayed only faint DBH-I. In a typical parenchymal cell cluster, most cells with strong DBH-I were irregular in shape and appeared to partially surround those with weak DBH-I which usually were rounded in contour. In the cat carotid body most parenchymal cells showed a strong to moderate DBH-I. In both the rat and cat carotid bodies varicose nerve fibres with DBH-I were associated primarily with blood vessels. All autonomic ganglion cells examined, which were associated with the rat carotid body, showed DBH-I. Electron microscopy revealed that most DBH-I in the strongly positive cells of the rat carotid body was associated with dense granules (possibly corresponding to dense-cored vesicles of various sizes), although some was found in other sites. In oval cells with less DBH-I, reactivity resided in some of the large granules. In the cat carotid body the glomus cells contained more granules of various sizes and shapes than did those of the rat carotid body. Most of the cat glomus cell granules exhibited DBH-I activity. Our results indicate that some of glomus cells in the rat and most of the glomus cells in the cat contain DBH and therefore may be sites of norepinephrine synthesis.

Animals↗