Psychosine cytotoxicity toward rat C6 glioma cells and the protective effects of phorbol ester and dimethylsulfoxide: implications for therapy in Krabbe disease

Psychosine cytotoxicity was tested as to its effects on rat C6 glioma cells. At a low concentration--below 40 microM--psychosine appeared to stimulate cell proliferation. Above the concentration range of 40 microM-60 microM, however, it showed a cytotoxic effect. When phorbol ester (PDB) or dimethylsulfoxide (DMSO) was supplemented to cultures being exposed to psychosine, the total number of live cells, protein content and CNPase activity dramatically increased as compared with the levels in cultures treated with psychosine alone. The results of these basic studies suggest another approach as to therapy for globoid cell leukodystrophy.

Development of resting membrane potentials of embryonic murine spinal cord cells evaluated by flow cytometric analysis

The membrane electrical properties of embryonic murine spinal cord cells of embryonic day-10 (E10) to E14 were studied using a voltage-sensitive oxonol dye combined with fluorescence-activated cell sorting techniques. This period of development corresponds to the time when neurons differentiate from their neuroblast precursors. Bovine oligodendrocytes were also investigated in these studies as they have an exclusive K+ dependence on resting membrane potential (RMP). Fluorescence emission histograms of spinal cord cells on E11-E14 exhibited little difference, suggesting that the RMP of cells of these ages were similar. Applications of Leiuris toxin, batrachotoxin, veratrine and veratridine, which modify sodium channel gating, produced shifts in the fluorescence histograms of cells on E12, E13 and E14 indicating membrane depolarization. The results indicated that RMP of spinal cord cells do not change appreciably between E11 and E14 and that the initial appearance of a voltage-dependent Na+ conductance occurs at E12.

Ion channels in cultured adult human Schwann cells

Single channel currents have been recorded from cultured adult human Schwann cells. In both cell-attached and -excised (inside-out) patches, openings from a high-conductance (360 pS) channel were observed; measurements of the zero-current potential indicated that the channel was predominantly selective for chloride. Depolarizing and hyperpolarizing voltage steps activated the anion channel, which subsequently reverted to a closed state even in the presence of the maintained step. A second channel, with a conductance near 20 pS and with a current amplitude that increased with patch hyperpolarization, passed inward K+ currents in both cell-attached and inside-out patches. The mean open times for this channel were near 20 ms at the cell resting potential and decreased with patch hyperpolarization. The presence of these anion and cation selective channels in the human Schwann cell membrane would be consistent with a role for the cells in the regulation of extracellular K+.

Expression and modulation of HLA-DR on cultured human adult astrocytes

Expression of Class II major histocompatibility complex (MHC) antigens on astrocytes has been implicated as contributing to the immune responses characteristic of chronic autoimmune diseases of the central nervous system. We examined the properties and regulation of HLA-DR on cultured human adult astrocytes. We found that a proportion of human astrocytes from each of fifteen individual donors expressed HLA-DR under basal culture condition; while this proportion differed among the human subjects (range 3-65%), the results for each individual remained relatively constant when analyzed at several time points (up to 125 days in vitro). Attempts to modulate HLA-DR expression by a variety of cytokines likely to be present in inflammatory infiltrates in the brain showed that only gamma-interferon could increase the proportion of human astrocytes that expressed HLA-DR. Whether the variability of HLA-DR expression on astrocytes between different individuals reflects a genetic trait which can influence susceptibility to autoimmune central nervous system diseases remains to be determined.

Neonatal mammalian spinal cord neurons and motoneurons in monolayer culture

Previously, embryonic tissues have been used to produce monolayer cultures containing mammalian spinal cord neurons (SCN) and motoneurons (MN) for studies of the pathophysiology of motoneuron diseases. We demonstrate here that viable SCN and MN were observed in dissociated cultures from neonatal rat and mouse. These SCN and MN produced neurites and expressed acetylcholinesterase, neuron-specific enolase and neurofilament protein. These results indicate that cultured postnatal SCN and MN are capable of survival, neurite extension, and phenotypic expression in culture.

Nucleotide sequence of the complementary DNA for turkey growth hormone

Near-full length complementary DNA (cDNA) clones encoding turkey growth hormone (GH) have been isolated from a pituitary library. The longer of the two turkey GH cDNA clones that were sequenced is 803 base pairs (bp) in length and contains 41 nucleotides of the 5'-untranslated region (UTR), an open reading frame of 648 bp that encodes a 25 amino acid leader polypeptide segment as well as a 191 amino acid mature turkey GH protein, and a 3'-UTR that is 92 bp long followed by a 22 bp poly A tract. Comparison of the turkey GH nucleotide sequence to that of other avian GH clones shows the coding region to be greater than 93% homologous while the homology to mammalian GH sequences is between 68 and 78%. Northern blot analysis showed an approximate 800 bp turkey GH processed mRNA transcript that hybridized to the turkey GH cDNA probe. A large up-regulation of turkey GH transcription occurred when intact cultured pituitaries were treated with 1 nM human growth hormone releasing hormone but only modest changes were observed when cultures were treated with thyroid releasing hormone or somatostatin.

Abnormality in cultured oligodendrocytes and Schwann cells isolated from the twitcher mouse

Oligodendrocytes and Schwann cells were isolated from the brain and dorsal root ganglia of the twitcher mouse, a murine model of Krabbe's disease (globoid cell leukodystrophy), and grown in tissue culture. Oligodendrocytes were cultured for up to 22 d in vitro and were immunostained with a galactocerebroside antibody, a specific marker for oligodendrocytes. The control oligodendrocytes developed well-branched processes and membrane sheets, whereas the twitcher oligodendrocyte had wirelike processes with no membrane expansion and progressive degeneration. Schwann cells from the twitcher could not extend their processes as long as normal counterparts. The amounts of psychosine in the enriched population of oligodendrocytes and Schwann cells from the twitcher mouse are about 50-fold and 70-fold higher, respectively, than those in the control cells. These data suggest that psychosine may play an important role in the progression of abnormal features of oligodendroglial membrane formation and in the absence of process elongation in Schwann cells in the twitcher mutant.

Neurobiology of human oligodendrocytes in culture

Enriched populations of oligodendrocytes were isolated from adult human brains of 3-15 hours postmortem using the trypsinin digestion-Percoll density gradient method and were cultured for an extended period of time up to 6 months. Cell type specific antigens that were expressed by oligodendrocytes were galactocerebroside, myelin basic protein, proteolipid protein, 2'3'-cyclic nucleotide 3'-phosphohydrolase and myelin-associated glycoprotein. In addition, HLA-A,B,C and HLA-DR, respectively, Class I and Class II antigens of the major histocompatibility complex, were demonstrated on oligodendrocytes. Three classes of gangliosides, GM1, GM4, and GD3, were also demonstrated on oligodendrocytes, while GM1 and GM4 gangliosides were detected on the surface of astrocytes. The presence of "transitional" or "bipotential" glial cells that were derived from oligodendrocytes and that expressed both oligodendroglial and astrocytic phenotypes was demonstrated. Treatment of the cells by cyclic AMP and its derivatives reversed this dual phenotypic expression back to the oligodendroglial trait. Electron microscopic examination of oligodendrocytes indicated that they were capable of synthesizing and assembling myelin sheaths in culture in the absence of any neuronal signal input.

Psychosine cytotoxicity in rat neural cell cultures and protection by phorbol ester and dimethyl sulfoxide

In Krabbe's disease (globoid cell leukodystrophy), galactosylsphingosine (psychosine) is considered to be a causative agent of the pathology found in the nervous system of the patients. In our study, we examined the cytotoxic effect of psychosine in neural cell cultures derived from the rat nervous system. The concentration of toxic thresholds varied from cell type to cell type. The 50% of toxic doses for oligodendrocytes, astrocytes, and the sensory neurons of the dorsal root ganglia were 8, 20, and 30 micrograms/mL, respectively. Oligodendrocytes, therefore, appeared to show a higher sensitivity to psychosine than did astrocytes or neurons. When phorbol ester or DMSO was applied simultaneously with psychosine as protective agents in enriched cultures of rat oligodendrocytes, the total number of live cells and galactocerebroside-positive cells and the 2'3'-cyclic nucleotide 3'-phosphohydrolase activity in these cultures were considerably higher as compared with their levels in the experimental cultures treated with psychosine alone. These results indicate that phorbol ester and DMSO could serve as protective agents for psychosine neurotoxicity.

Transfection and stable transformation of adult mouse Schwann cells with SV-40 large T antigen gene

Cultured Schwann cells derived from adult mouse dorsal root ganglia and peripheral nerves were transfected with a plasmid containing SV-40 large T antigen gene, and 25 colonies of stable transformants were obtained, one of which was expanded and recloned. This transfected cell line, designated MS1, expressed SV-40 large T antigen and showed continuous cell growth with a doubling time of 27 hours. The MS1 cells had distinct Schwann cell phenotypes such as S-100 protein, laminin, 2',3'-cyclic nucleotide 3'-phosphodiesterase and P0 protein, as shown by immunofluorescence microscopy. When MS1 cells were exposed to dibutyryl cyclic adenosine-3',5'-monophosphate (dbc AMP), they extended long bipolar processes two- to ten-fold longer than those of untreated MS1 cells and frequently formed whorl-like alignments similar to palisade formations or organoid patterns observed in human Schwannomas and neurofibromas. These results suggest that transformed Schwann cells can be a useful model for analyzing regulatory mechanisms of Schwann cells, neuron-Schwann cell interactions and experimental Schwann cell neoplasms in vitro.

Synthesis and alpha 2-adrenoceptor effects of substituted catecholimidazoline and catecholimidazole analogues in human platelets

It is known that the steric requirements for the interactions of catecholamines and catecholimidazolines with alpha 1- and alpha 2-adrenoceptors are different. New analogues of desoxycatecholimidazoline (1), desoxycatecholimidazole (3), benzylic hydroxyl substituted imidazole (4), and the aromatic fluorine substitution analogues of 1 at the 2 (5), 5 (6), and 6 (7) positions, and a set of asymmetric 4-substituted catecholimidazolines, S-8 and R-8, were prepared and tested for interaction with alpha 2-adrenoceptors in human platelets. With the exception of 3, all compounds were selective for alpha-adrenoceptor-mediated responses in human platelets. Introduction of a double bond in imidazoline 1 to give an imidazole 3 or the introduction of a benzylic hydroxyl group to 3, as in 4, reduced the inhibition of platelet aggregation with a rank order potency of 1 greater than 3 greater than 4. Fluorine atom substitution at the 2-, 5-, or 6-positions only slightly modified the inhibitory activity of 1. Each analogue (1, 3-7) produced alpha 2-mediated inhibition of platelet adenylate cyclase and can be classified as a partial agonist. The inhibition potency of S-8 and R-8 against epinephrine-induced aggregatory responses were greatly different, and only R-8 and 4 were alpha 2-agonists on human platelet function. Our studies provide further evidence for the differential interaction of catecholamines and catecholimidazolines in alpha 1- and alpha 2-adrenoceptor systems.

Absence of natural killer (NK) cell activity against oligodendrocytes in multiple sclerosis

The cytotoxicity of natural killer (NK) cells directed to enriched cultures of bovine oligodendrocytes was investigated in multiple sclerosis (MS) patients and controls. Macrophage-depleted peripheral blood lymphocytes were used as effector cells in a 4-h 51Cr release assay. No significant cytotoxic activity to oligodendrocytes was identified in either MS or control groups. In contrast, a definite cytotoxic activity directed toward K562 cells was observed in the study populations. No statistically significant difference was observed between chronic progressive or stable MS, other neurological diseases (OND), and normal controls. These results indicate that NK cell activity directed toward intact bovine oligodendrocytes is not significantly different between MS and control groups and question the significance of studies employing K562 cells as the target in NK assays in MS. Furthermore, these observations suggest that NK-mediated cytotoxicity against oligodendrocytes is unlikely to be a specific mechanism mediating demyelination in MS.

Transplantation of human sympathetic neurons and adrenal chromaffin cells into parkinsonian monkeys: no reversal of clinical symptoms

Cultured human fetal sympathetic ganglion explants or adrenal chromaffin cell aggregates were implanted into the left striatum of monkeys whose left nigrostriatal pathway had been lesioned with the neurotoxin MPTP. There was no clinical reversal of parkinsonian symptoms and PET scans did not show increased striatal fluorodopa uptake from pre-implant levels. At sacrifice, left striatal contents of dopamine were not statistically different from MPTP-treated but non-implanted controls. Histological examinations revealed pockets of extrinsic cells which were found at the end of needle tracks. There was no evidence of immune rejection. The extrinsic cells did not stain for tyrosine hydroxylase or neurofilament, suggesting that they were not dopaminergic neurons. The failure to reverse clinical parkinsonian symptoms highlights the stage of infancy of neural implantation in Parkinson's disease.

Human and simian glial cells infected by human T-lymphotropic virus type I in culture

Although human T-lymphotropic virus type I (HTLV-I) has been implicated in the etiology of tropical spastic paraparesis (TSP) and HTLV-I associated myelopathy (HAM), the direct infectivity of the virus against constituent cells in the central nervous system remains undetermined. To investigate the neurotropism of HTLV-I, we exposed cultured human and simian glial cells to HTLV-I. Primary mixed glial cell cultures of astrocytes and oligodendrocytes were obtained from adult human and cynomolgus monkey (Macaca fascicularis) brains by an enzyme digestion-Percoll gradient method. After two weeks in vitro, the cells were co-cultured with irradiated MT-2 cells, an HTLV-I-producing T-cell line. Cultures were double stained with antibodies against cell-type specific markers and anti-HTLV-I p19 (gag) monoclonal antibody. The HTLV-I antigen was demonstrated in small numbers of glial fibrillary acidic protein-positive cells (astrocytes) and galactocerebroside-positive cells (oligodendrocytes) in both the human and simian cultures. Electron microscopy demonstrated the presence of type C virus-like particles in the cytoplasm of astrocytes. These results indicate that HTLV-I is capable of infecting human and simian glial cells in vitro.

Purification and characterization of the sopB gene product which is responsible for stable maintenance of mini-F plasmid

The mini-F plasmid has the trans-acting sopA, sopB genes and the cis-acting sopC DNA which are essential for plasmid partitioning. In this paper, we report the purification of the sopB gene product from extracts of cells harboring a pBR322 derivative carrying the sopB gene. The purity of the final preparation was more than 95%, as determined by densitometry. The amino acid sequence of the amino-terminal region of the protein for the 17 residues identified was identical to that predicted from the DNA sequence of the sopB gene. Therefore, it was concluded that the protein was the sopB gene product. Using anti-SopB serum, the SopB protein was detected in the cell lysates of F+, F', and Hfr strains. The SopB protein bound to the plasmid DNA of a pBR322 derivative carrying the sopC DNA segment, but not to the vector plasmid pBR322.

Phagocytic activity of human adult astrocytes and oligodendrocytes in culture

The phagocytic activity of human glial cells was examined in primary cultures obtained from normal human brain obtained at autopsy. Highly enriched cultures of astrocytes and oligodendrocytes were established using an enzyme digestion-Percoll density gradient method. These cultures were exposed to medium containing carbon particles (indian ink) for one-24 hours. Under phase contrast and immunofluorescence microscopy, carbon particles were demonstrated in the cytoplasm and processes of both astrocytes and oligodendrocytes. Electron microscopic examination revealed carbon particles phagocytized and segregated in these cells. These findings may support a view that both astrocytes and oligodendrocytes participate in phagocytosis in certain neurological diseases.

Somatostatin increases intracellular Ca2+ concentration in cultured rat hippocampal neurons

Changes of intracellular Ca2+ concentration [( Ca2+]i) in response to somatostatin were measured in cultured rat hippocampal neurons on a single cell basis by fura-2 fluorometry. Somatostatin increased [Ca2+]i dose-dependently and this effect was completely blocked in either Ca2+-depleted medium or LaCl3-containing medium. In addition, omega-conotoxin GVIA completely inhibited the effect of somatostatin. Our results indicate that somatostatin receptors couple with N-type voltage-sensitive Ca2+ channels in cultured rat hippocampal neurons.

Existence of inward potassium currents in adult human oligodendrocytes

We report the first measurements of single channel currents in cultured adult human oligodendrocytes, obtained postmortem. The channels selectively pass potassium inwardly and possess properties which would be suitable for a physiological role for oligodendrocytes in the human brain as part of a regulatory mechanism for maintenance of extracellular potassium concentration near active neurons. These properties include a long mean open time near normal resting potential and a marked dependence of membrane depolarization to increase the channel open time which could be an important factor when the driving force for inward potassium movement was small. Furthermore, the properties of these potassium channels are remarkably similar to those of channels previously observed in adult bovine oligodendrocytes, which supports the use of animal data to describe function in the human brain.

Immunofluorescence demonstration of neurofilament polypeptide expression in fetal human neurons in culture

Sensory neurons from 10-week human fetal dorsal root ganglia were dissociated and grown in vitro and immunostained with monoclonal antibodies specific for neurofilament triplet polypeptides (non-phosphorylated 70 kDa peptide, NF-L; phosphorylated 150 kDa peptide, NF-M; and phosphorylated 200 kDa peptide, NF-H). All 3 neurofilament subunits appeared early in neuronal perikarya, but they were demonstrated in neurites at different times of culture. The phosphorylated 150 kDa subunit was the first to be expressed in neurites and was followed first by the phosphorylated 200 kDa subunit, and then by the 70 kDa subunit.

[Recent advances in neural cell culture]

Cells isolated from the avian and mammalian central and peripheral nervous system and cultured in vitro provide an opportunity to study in situ properties of neurons and glial cells under relatively simple and carefully controlled conditions. Since Harrison's success in maintaining in vitro embryonic frog spinal cord 80 years ago, neural tissue culture has developed into an important and versatile discipline of neuroscience. The techniques developed in the past fall into four broad classes: Explant cultures, which are explanted from specific neuroanatomic loci to substrates as small tissue fragments. Dissociated cell cultures, which involve the seeding of enzymatically or mechanically dispersed cells on various attachment substrates. Reaggregate cultures, which require re-association of dissociated cells into small aggregates. Purified cell populations, which are prepared by the isolation of different cell types by gradient centrifugation or other separation techniques. These cultures have been utilized in studying various aspects of brain development and function. In this review several areas of significant and stimulating development in neural cell culture have been documented. They include formulation of serum-free medium, effects of growth factors, utilization of cell type-specific markers, and isolation and culture of purified neuronal/glial cells.

Potent antiplatelet effects of cyclic clofibric acid (CPIB) analogs on human platelets

CPIB possesses antiplatelet as well as hypolipidemic activities. Two cyclic CPIB analogs, 6-phenylchroman-2-carboxylic acid (PCCA) and 6-cyclohexylchroman-2-carboxylic acid (CHCCA) were also found to be antagonists of the prostaglandin (PG)-dependent pathway of human platelet activation. PCCA and CHCCA were inhibitors of aggregation (AGG) and secretion (SEC) induced by ADP or epinephrine (E) [second waves only] and arachidonic acid (AA) with IC50 values ranging from 2.3-8.7 microM for PCCA and 3.7-12.1 microM for CHCCA. Neither compound antagonized the proaggregatory effects of the thromboxane A2 (TXA2) receptor agonist, U46619. CPIB blocked ADP and E-induced AGG and SEC (IC50's greater than 1200 microM) but not AA- or U46619-induced responses. Only CPIB blocked thrombin-induced AA release. Data showed that PCCA and CHCCA inhibited AA-induced malondialdehyde formation (IC50's = 9.3 and 11.3 microM, respectively) and thrombin-induced production of prostaglandin E2, prostaglandin F2 alpha, and TXB2 with IC50's ranging from 2.9 to 13.4 microM. PCCA and CHCCA were at least 200- to 500-fold more potent than CPIB as inhibitors of the PG-dependent pathway of human platelet activation. We conclude that PCCA and CHCCA act by inhibiting platelet cyclooxygenase activity whereas CPIB blocks the activity of phospholipase A2. Hypolipidemic PCCA and CHCCA represent a potent class of cyclooxygenase inhibitors which may be more useful than CPIB for treatment of atherosclerotic and thrombotic disorders.

Human fetal Schwann cells in culture: phenotypic expressions and proliferative capability

In this report we examined the phenotypic expressions and the proliferative capability of cultured human fetal Schwann cells. Antigens that were expressed included laminin, nerve growth factor receptor, neural cell adhesion molecule, S-100 protein, and that recognized by the monoclonal antibody HNK-1. In addition, HLA-A,B,C and HLA-DR, respectively, class I and class II antigens of the major histocompatibility complex, were demonstrated on Schwann cells. Mitotic capability was high, with an average of 34% of Schwann cells undergoing proliferation over a 2-day period.

Single channel potassium currents in cultured adult bovine oligodendrocytes

These studies have enabled the first characterization of the properties of ion channels in adult oligodendrocytes. Cell-attached recordings from cultured adult bovine cells showed channel activity with 140 mM KCl in the patch pipette; the amplitude of the currents was increased with increasing membrane hyperpolarization. This channel, with a conductance of 29 pS, was selective for inward K+ current; little or no outward current was measured for large depolarizing voltage steps. The channel open time was strongly dependent upon membrane potential, with membrane hyperpolarization decreasing the mean open time 100-fold over a range of 80 mV; at the resting potential of the cell the mean open time of the channel was in excess of 50 ms. Decreasing the concentration of K+ in the pipette diminished the channel conductance with no significant effect to alter the channel open time dependence on potential. The rectification and kinetic properties of the channel would be consistent with a physiological role for the channel in the regulation of external K+ near active neurons; in particular the effect of membrane depolarization to cause maintained channel open duration could be important when the driving force for inward potassium movement through oligodendrocyte membrane was low. Channels selective for outward potassium movement were seen with inside-out excised patch recordings with symmetrical potassium concentrations across the patch; the density of these channels in the bovine membrane was low.

Tissue culture study of adult human retina neurons

Explant cultures were established from adult human retina tissues obtained from 20 individuals (age range 19-79), 7-45 hr postmortem, and maintained for the period of up to 4 months. Forty percent of these cultures (eight out of 20 cases) produced healthy and viable cultures as judged by phase contrast microscopy and by electron microscopy. Phase contrast microscopic examination of living cultures showed that the early outgrowths of the explants consisted of flat fibroblasts migrating out from the edge of the explants. For the next 2-4 weeks, a large population of small spherical or ovoid cells possessing thin processes was found in the areas of the outgrowth. Electron microscopic examination of cultures revealed the survival of photoreceptors, neurons and synapses with well preserved ultrastructures. This communication is the first to describe the successful culture of adult human CNS neurons in general and adult human retina neurons in particular. This culture system is ideally suited to investigate the effects of infective or toxic agents suspected of causing retinal pathology in human eye diseases.