Membrane properties of identified embryonic nerve and glial cells of the leech central nervous system

Summary The membrane potential of identified nerve (Retzius) cells and neuropil glial cells from 11 (±1) day-old embryos of the leechHirudo medicinalis was recorded using conventional intracellular microelectrodes. At this stage all ganglia of the segmental nervous system are formed. The membrane potential of Retzius cells was –68±4 mV (±SD,n=8), and showed a slope of 42 mV between 10 mM and 100 mM external K concentration. Retzius cells were able to fire action potentials which had a fast Na-dependent component, and, under appropriate conditions, also generated slow Ca (Ba) action potentials. The mean membrane potential of the neuropil glial cell at physiological K concentration (4 mM) was –83±5 mV (±SD,n=10), and showed a dependence of 56 mV for a tenfold change in the external K concentration (> 4mM). Neuropil glial cells showed no signs of voltage-activated excitability, but they repeatedly depolarized in the presence of 0.1 mM 5-HT.     

Possible role of somatotropic hormone in regulating the functional state of glial cells in the central nervous system

Experiments were made to study the actions of STH and its fragment capable to stimulate the growth processes on MAO activity and selective binding of catecholamines by alpha- and beta-adrenoreceptors in glial cells of the rat brain cortex. For comparison the effects of STH and its fragment on 3H-PGE1 binding were studied. STH and its fragment were found to produce no influence on MAO activity or specific binding of 3H-PGE1 with glial cells. STH and its fragment (5.10(-9) M) were found to reduce specific binding of 3H-dihydroergocryptine with beta- and alpha-adrenoreceptors of glial cells, respectively. It is suggested that STH and its fragment can modulate the function of glial cells by changing the selective action of catecholamines on subpopulations of adrenergic receptors.     

Direct measurement of intracellular pH in identified glial cells and neurones of the leech central nervous system

Neutral carrier pH-sensitive double-barrelled microelectrodes were used to investigate intracellular pH (pHi) in leech neuropile glial cells and in Retzius neurones. The mean pHi of the glial cells was 6.87 +/- 0.13 (+/- SD, n = 27) in HEPES-buffered saline (pHo 7.4) and 7.18 +/- 0.19 (n = 13) in solutions buffered with 2% CO2- 11 mM HCO3-. The distribution of H+ ions in both the glia and neurones was found not to be in electrochemical equilibrium. To investigate pHi regulation, the pHi was decreased by exposure to CO2 or by adding and then removing NH4Cl. Acidification by any method was followed by a recovery to normal pHi values within minutes. The pHi recovery from acidification in neuropile glial cells in HEPES-buffered saline and CO2-HCO3- buffered saline was, however, blocked by removing external Na. In HCO3(-)-free solutions the diuretic amiloride (2 mM) reduced the rate of pHi recovery. In the presence of HCO3-, the rate of acid efflux was stimulated; the stilbene 4-acetamido-4'-isothiocyanatostilbene-2,3'-disulfonic acid (SITS; 0.5 mM) slowed pHi recovery. In HEPES buffered and CO2-HCO3- buffered solutions pHi regulation in neurones was inhibited by removing external Na. In HCO3(-)-free solutions amiloride reduced the rate of pHi recovery considerably. In the presence of HCO3-, SITS or amiloride slowed but did not completely block pHi recovery. We conclude that leech glial cells and neurones have two mechanisms of pHi regulation, one being Na+-H+ exchange and the other Na+ and HCO3- dependent.     

Biochemically differentiated clonal human glial cells in tissue culture

A clonal line of astrocytes (designated CHB) derived from a brain tumor of human origin has been established in tissue culture. This cell line is capable of synthesizing an acid protein unique to the nervous system (S100-protein). The S100-protein synthesized by CHB cells is immunologically indistinguishable (by micro-complement fixation) from S100-protein present in human brain.     

Effects of opioid peptides and naloxone on tissue from the central and peripheral nervous system in culture

A study was made of the effects of opioid peptides (leu-enkephalin and dalargin AE-1, its synthetic analog) and of naloxone, an opiate receptor blocker, on organotypic cultures of spinal cord and spinal ganglia cells. The cellular composition and size of explant outgrowth was estimated according to in vitam morphological observations. It was found that all the opioid peptides tested at concentrations of 10^–9-10^–10M exercise a clear-cut growth-promoting effect on cultures from the spinal cord as well as those from the peripheral nervous system [4, 5]. Naloxone at a concentration of 10^–5-10^–6 M does not block peptide action, but itself stimulates growth. It was also proved that opioid peptides act as trophic factors for spinal ganglia nerve cells, increasing their survival in culture. Endorphins can thus serve as growth factors for tissues of the peripheral as well as the central nervous system. The likely processes lying at the root of the growth-promoting and trophic effects of endorphins on nerve tissue are discussed.Institute of Experimental Cardiology of the All-Union Cardiological Research Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 2, pp. 227–233, March–April, 1986.     

Gross morphology of the central nervous system of a phytoseiid mite

The general morphology of the central nervous system is analysed in intact females of the predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae), using a nucleic acid label (YOYO-1) and confocal laser scanning microscopy. The somata of all cells that comprise the synganglion reside in the cortex. The cortex harbours an estimated total of 10,000 cells. The somata are densely packed in the cortex and cells residing in the inner cortex may only occupy about 1.8 μm. As in all Arachnida, the synganglion is divided in a sub- and a supra-oesophageal nervous mass. Both the cortex and the neuropil appear continuous between these two nervous masses. The sub-oesophageal nervous mass mainly consists of the four paired pedal ganglia that are each associated with a leg. The prominent olfactory lobes are ventrally associated with the first pedal ganglia. A small opisthosomal ganglion occupies the most caudal part of the sub-oesophageal ganglion. The rostral part of the supra-oesophageal nervous mass consists of the paired cheliceral and palpal ganglia. The supra-oesophageal ganglion is the largest ganglion in the supra-oesophageal nervous mass and unlike all other ganglia it is not associated with any of the major nerves. It is therefore more likely involved in secondary information processing.     

An approach for the separation of mononuclear inflammatory cells from central nervous system tissue

It is not known whether currently available methods separate lymphoid cells from nervous system sites of immunologic disorders without the selective enrichment or depletion of particular cell subpopulations. To test the validity of a cell separation technique we developed, we applied this technique to a mixture of guinea pig blood mononuclear cells already characterized for surface membrane characteristics with autologous spinal cord tissue. Using this method, 10–20% of the original blood cell population was recovered. The percentages of E-rosetting and surface immunoglobulin cells in the separated cells was quite similar to that in the added blood cells. EAC-rosetting cell percentages were somewhat lower. This method shows promise for the in vitro study of cells obtained from lesions of autoimmune diseases in the central nervous system.     

Self propagation of injured tissue by localized changes of free radicals in the central nervous system.

To examine the role of free radicals in the pathogenesis of injured tissue in the central nervous system (CNS), we developed a new technique for mapping superoxide free radicals, vascular permeability, and energy metabolism simultaneously. The distribution of superoxide anions in the CNS is based upon the 380 nm chemiluminescence of 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2a] pyrazin-3-one (CLA-phenyl) when it reacts with superoxide anions in frozen tissue sections. This new CLA-phenyl hybrid--paper technique show clear relationships between the regional production of superoxide free radicals, increased vascular permeability, and changes of energy metabolism in the self propagating phenomena occurring in the various lesions in the CNS.     

Stem cells in the adult mammalian central nervous system

Over the past year, evidence has accrued that adult CNS stem cells are a widespread progenitor cell type. These cells may normally replace neurons and/or glia in the adult brain and spinal cord. Advances have been made in understanding the signals that regulate stem cell proliferation and differentiation. A deeper understanding of the structure of germinal zones has helped us move towards identifying stem cells in vivo. Recent studies suggest that the fate of stem cell progeny in vivo may be linked to the complexity of the animal's environment.     

Cancer stem cells in the mammalian central nervous system

Malignant tumours intrinsic to the central nervous system (CNS) are among the most difficult of neoplasms to treat effectively. The major biological features of these tumours that preclude successful therapy include their cellular heterogeneity, which renders them highly resistant to both chemotherapy and radiotherapy, and the propensity of the component tumour cells to invade, diffusely, the contiguous nervous tissues. The tumours are classified according to perceived cell of origin, gliomas being the most common generic group. In the 1970s transplacental administration of the potent neurocarcinogen, N-ethyl-N-nitrosourea (ENU), enabled investigation of the sequential development of brain and spinal neoplasms by electron microscopy and immunohistochemistry. The significance of the primitive cells of the subependymal plate in cellular origin and evolution of a variety of glial tumours was thereby established. Since then, the development of new cell culture methods, including the in vitro growth of neurospheres and multicellular tumour spheroids, and new antigenic markers of stem cells and glial/neuronal cell precursor cells, including nestin, Mushashi-1 and CD133, have led to a reappraisal of the histological classification and origins of CNS tumours. Moreover, neural stem cells may also provide new vectors in exciting novel therapeutic strategies for these tumours. In addition to the gliomas, stem cells may have been identified in paediatric tumours including cerebellar medulloblastoma, thought to be of external granule cell neuronal derivation. Interestingly, while the stem cell marker CD133 is expressed in these primitive neuroectodermal tumours (PNETs), the chondroitin sulphate proteoglycan neuronal/glial 2 (NG2), which appears to denote increased proliferative, but reduced migratory activity in adult gliomas, is rarely expressed. This is in contrast to the situation in the histologically similar supratentorial PNETs. A possible functional 'switch' between proliferation and migration in developing neural tumour cells may exist between NG2 and ganglioside GD3. The divergent pathways of differentiation of CNS tumours and the possibility of stem cell origin, for some, if not all, such neoplasms remain a matter for debate and continued research, but the presence of self-renewing neural stem cells in the CNS of both children and adults strongly suggests a role for these cells in tumour initiation and resistance to current therapeutic strategies.