摘要:

A quantitative histochemical method was developed to determine aldehyde dehydrogenase (EC 1.2.1.3; ALDH) activity in the CNS. The distribution of ALDH activity in all rat brain and spinal cord regions is described. Among the CNS neuron structures, high enzyme activity was found in receptor and effector neurons, whereas low activity was noted in perikarya of the majority of intermediate neurons, including all aminergic neurons. A positive correlation was demonstrated between the distribution of ALDH activity among rat CNS microregions (our own data) and the density of dopaminergic terminals, dopamine content, and monoamine oxidase activity (literature data) among the same microregions. They may reflect a spatial linkage between ALDH and the predicted sites of natural aldehyde production. Lower enzyme activity was found in phylogenetically younger brain structures. It may explain the differential resistance of CNS structures to ethanol (acetaldehyde). Among the barrier CNS structures, moderate ALDH activity was found in capillaries and surrounding astrocytes and high activity was noted in ependimocytes covering the brain cavities and those of the vascular plexus. This provides realization of the function of ALDH as a brain metabolic barrier for aldehydes.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02555.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:Cell surface binding, internalization, and biological effects of insulin‐like growth factors (IGFs) I and II have been studied in primary neuronal cultures from developing rat brain (embryonic day 15). Two types of IGF binding sites are present on the cell surface. The IGF‐I receptor α‐subunit (Mr125,000) binds IGF‐I with aKDof 1 nMand IGF‐II with 10 times lower affinity. The mannose‐6‐phosphate (Man‐6‐P)/IGF‐II receptor (Mr250,000) binds IGF‐II with aKDof 0.5 nMand IGF‐I with 100 times lower affinity. Surface‐bound IGF‐I and IGF‐II are internalized by their respective receptors and degraded to amino acids. Man‐6‐P increases the receptor binding and internalization of IGF‐II but not those of IGF‐I. Neuronal synthesis of RNA and DNA is increased twofold by IGF‐I with 10 times higher potency than IGF‐II. Antibody 3637, which blocks receptor binding of IGF‐II, has no effect on the DNA response to IGF‐I or IGF‐II. Double immunocytochemical staining with antibodies to bromodeoxyuridine and neurofilament shows that>80% of the bromodeoxyuridine‐positive cells become neurofilament positive. It is concluded that IGF‐I and IGF‐II bind to two receptors on the surface of neuronal precursor cells that mediate endocytosis and degradation of IGF‐I and IGF‐II. Proliferation of neuronal precursor cells is stimulate

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02556.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:The concentration of dopamine (DA) in the synaptic cleft in the mouse striatum in vivo was estimated from the competition between the synaptic DA and the3H‐labelled DA D2 receptor agonistsN‐n‐propylnorapomorphine (NPA) orN,N‐diethyl‐N′‐[(3α,4aα,10β)‐1,2,3,4,4a,5,10,10a‐octahydro‐7‐hydroxyl‐1‐propyl‐3‐benzo (g) quinolinyl]sulfamide (Sandoz 205–501) injected intravenously in tracer doses. Knowing the inhibitor constant for DA in inhibiting the binding of these receptor agonists in vitro, attempts were made to calculate the changes in the synaptic DA concentration from the changes in the in vivo binding of the receptor agonists evoked by various pharmacological agents. Inhibiting the firing of the dopaminergic neurons by γ‐butyrolactone (GBL) increased the binding of the receptor agonists corresponding to a decrease in the synaptic DA concentration of 55 ± 2 nMin the experiments with [3H]Sandoz 205–501 and 48 ± 3 nMin the experiments with tracer doses of [3H]NPA. These values may therefore approximate the normal DA concentration in the synaptic cleft in the mouse striatum. With this technique it was also possible to determine the synaptic concentration of NPA by its competition with [3H]Sandoz 205–501 for the DA D2 receptors in the striatum of GBL‐treated mice in vivo. To compare the estimated synaptic concentration of DA with the affinity of DA to D1 and D2 receptors and to the DA transporter in the mouse striatum the kinetic parameters were determined at 37°C in vitro. The Kivalue for DA in inhibiting the binding of ligands to the agonist sites of the D1 receptors (30–40 nM) was about one‐third of that of the D2 receptors (80–120 nM). TheKmvalue of the initial uptake of [3H]DA into synaptosomes from the mouse striatum was 209 ± 20 nM(n = 3) and theVmaxwas 7.00 ± 1.29 nmol/g tissue/min. Comparison of the affinities of DA for the D1 and D2 receptors with the synaptic DA concentrations shows that a considerable proportion of the receptors is occupied by DA under these conditions, wh

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02557.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:Molecular species of phosphatidylcholine containing unsaturated (i.e., monoenoic and polyenoic) 32‐ to 40‐carbon (very long chain) fatty acids (VLCFA‐PC) are present in normal human brain, the fatty acid composition changing significantly with development. There is a marked increase in the concentration and a change in the polyenoic VLCFA composition of these molecular species in brains of patients with inherited defects in peroxisomal biogenesis [Zellweger's syndrome, neonatal adrenoleukodystrophy (ALD), and infantile Refsum's disease]. In contrast, there is a marked increase in monoenoic VLCFA‐PC in X‐linked ALD whereas molecular species containing polyenoic VLCFA are minor c

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02558.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:Chronic liver failure induced by portocaval anastomosis (PCA) in Wistar rats resulted in a dramatic increase in histamine concentration in hypothalamus and a smaller, but clearly pronounced, elevation in the rest of brain. Between 10 and 120 days following surgery, shunted rats exhibited a histamine level 2.4‐ to 13‐fold higher in hypothalamus and 1.5‐ to 2.5‐fold higher in the rest of brain as compared to their control, sham‐operated pairs. There were no significant changes in histamine concentration in the other examined tissues. The increase in brain histamine could not be attributed to the inhibition of its degradation, because activity of histamineN‐methyltransferase remained unchanged for at least 40 days. Although the activity of histidine decarboxylase also remained unchanged when measured at a saturating concentration of L‐histidine, the increase in histamine content in brain seems to be due to its enhanced synthesis brought about by increased availability of L‐histidine in the tissue, as indicated by two to four times higher concentrations of this amino a

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02559.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:We have reported recently that prostaglandin E2(PGE2) stimulated phosphoinositide metabolism in bovine adrenal chromaffin cells and that PGE2and ouabain, an inhibitor of Na+,K+‐ATPase, synergistically induced a gradual secretion of catecholamines from the cells. Here we examined the involvement of a GTP‐binding protein(s) in PGE receptor‐induced responses by using NaF. In the presence of Ca2+in the medium, NaF stimulated the formation of all three inositol phosphates, i.e., inositol monophosphate, bisphosphate, and trisphosphate, linearly over 30 min in a dose‐dependent manner (15–30 mM). This effect on phosphoinositide metabolism was accompanied by an increase in cytosolic free Ca2+. NaF also induced catecholamine release from chromaffin cells, and the dependency of stimulation of the release on NaF concentration was well correlated with those of NaF‐enhanced inositol phosphate formation and increase in cytosolic free Ca2+. Although the effect of NaF on PGE2‐induced catecholamine release in the presence of ouabain was additive at concentrations below 20 mM, there was no additive effect at 25 mMNaF. Furthermore, the time course of catecholamine release stimulated by 20 mMNaF in the presence of ouabain was quite similar to that by 1 μMPGE2, and both stimulations were markedly inhibited by amiloride, with half‐maximal inhibition at 10 μM.Pretreatment of the cells with pertussis toxin did not prevent, but rather enhanced, PGE2‐induced catecholamine release over the range of concentrations examined. These results demonstrate that NaF mimics the effect of PGE2on catecholamine release from chromaffin cells and suggest that PGE2‐evoked catecholamine release may be mediated by the stimulation of phosphoinositide metabolism through a putative GTP‐binding protein insensi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02560.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:The effect of 2‐(4‐phenylpiperidino)cyclohexanol (AH5183 or vesamicol), a compound known to block the uptake of acetylcholine (ACh) into cholinergic synaptic vesicles, on the release of endogenous and [14C]ACh from slices of rat striatum was investigated. ACh release was evoked either by electrical stimulation or by veratridine. The effect of electrical stimulation was entirely dependent on external Ca2+. By contrast, veratridine (40 μM) also enhanced ACh release in the absence of Ca2+. Indeed, with veratridine two components were clearly distinguished: one dependent on external Ca2+and the other not. Vesamicol inhibited [14C]ACh release evoked by both veratridine and electrical stimulation in the presence of external Ca2+, provided it was added to the tissue prior to loading with [14C]choline. With the same treatment vesamicol only slightly affected the release of endogenous ACh. Under the same conditions the Ca2+‐independent [14C]ACh release evoked by veratridine was not prevented by vesamicol. The differential responsiveness to vesamicol suggests that ACh pools involved in Ca2+o‐dependent ACh release are different from those mobilized during Ca2+o‐independent A

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02561.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:Cerebellar granule cells were cocultured with astrocytes from either cerebral cortex or cerebellum in two different systems. In one system the cells were plated next to each other only sharing the culture medium (separated cocultures) and in the other system the granule cells were plated on top of a preformed layer of astrocytes (sandwich cocultures). Using astrocytes from cerebellum, granule cells developed morphologically and functionally showing a characteristic high activity of the glutamate synthesizing enzyme aspartate aminotransferase (AAT) as well as a high stimuluscoupled transmitter release regardless of the culture system, i.e., granule cells could grow on top of cerebellar astrocytes as well as next to these cells. In the case of cerebral cortex astrocytes it was found that cerebellar granule cells did not develop (11% survival) when seeded on top of these astrocytes. This was indicated by the morphological appearance of the cultures as well as by a negligible difference between the AAT activity in sandwich cocultures and astrocytes cultured alone. On the other hand, granule cells in separated cocultures with cerebral cortex astrocytes exhibited a normal morphology and a high activity of AAT as well as a large stimulus‐coupled transmitter release. Cerebellar and cortical astrocytes expressed the astrocyte specific enzyme glutamine synthetase in a glucocorticoid‐inducible form regardless of the culture system. The results show that under conditions of direct contact between granule cells and astrocytes, regional specificity exists with regard to neuron‐glia contacts. This specificity does not seem to involve soluble factors present in the culture medium because in separated cocultures the cerebellar granule cells developed normally regardless of the regional origin of the astro

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02562.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:In earlier studies, a 75,000‐dalton glycoprotein (gp75) has been identified as a component of both low‐ and high‐affinity nerve growth factor (NGF) receptors (NGFRs). Using an amphoteric expression vector, we have introduced the cDNA encoding the human gp75 into two neuroblastoma cell lines. SHEP is a human neuroblastoma cell line that lacks most neuronal characteristics and does not express NGFRs. The transformant line SHEP/NGFR expressed a single affinity class of NGF binding sites, did not display NGF‐induced up‐regulation offosoncogene expression, and did not efficiently internalize NGF. LANS is a neuroblastoma cell line with neuronal characteristics, including expression of neurofilament and display of short neurites. This cell line expresses a small number of high‐affinity NGFRs but no detectable low‐affinity sites. The transformant line LAN5/NGFR expressed both high‐ and low‐affinity NGFRs, displayed NGF‐induced up‐regulation offosoncogene, and efficiently internalized NGF. The number of high‐affinity NGF binding sites was nearly the same for LAN5 and LAN5/NGFR, a finding suggesting that there is a limiting number of some separately coded factor or subunit that is required for high‐affinity NGFRs. Because NGF induction offosoncogene expression correlated with expression of high‐affinity NGFRs, the putative second factor may al

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02563.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract:Phosphorylation of striatal membranes by cyclic AMP‐dependent protein kinase resulted in a reduction in the affinity of the D2dopamine receptor toward its agonistN‐propylnorapomorphine while the affinity to D2‐specific antagonists remained unchanged. The inhibitory effects observed by phosphorylation and guanine nucleotides on agonist binding to the D2receptor were additive. The purified D2dopamine receptor from bovine striatum was specifically phosphorylated by cyclic AMP‐dependent protein kinase with an apparent stoichiometry of 0.7 mol phosphate/mol receptor. The phosphorylated purified D2receptor also exhibited a reduced agonist binding activity with no change in antagonist binding. The action of cyclic AMP‐dependent protein kinase on both the membrane preparation and the purified D2receptor was inhibited by a specific inhibitor of the kinase. These data indicate that phosphorylation mediated by cyclic AMP‐dependent protein kinase may represent a physiological pathway for modulation of the receptor bindi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1991.tb02564.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY