Enzyme-linked immunosorbent assay of the D2-glycoprotein

Neural cell adhesion molecule (NCAM) and prealbumin in cerebrospinal fluid from depressed patients

The size of the soluble form of the human cerebrospinal fluid (CSF) neural cell adhesion molecule, NCAM-sol, was by gel permeation chromatography estimated to 160-250 kDa. Within the CSF the concentration of NCAM-sol was found about 15-25% increased in lumbar fluid and 25% increased in ventricular fluid, both compared to cisternal fluid. Whereas prealbumin was found evenly distributed in CSF, albumin was relatively enriched in lumbar fluid. The concentrations of NCAM-sol and prealbumin were measured in lumbar CSF from psychiatric patients. Prealbumin was increased 7.2% and NCAM-sol was decreased 15.1% in depressed patients. The changes were partially normalized during recovery from the depression. The findings can be explained by hypothesizing that endogenous depression is associated with an increased choroid plexus activity and CSF production.

Olfactory learning-related NCAM expression is state, time, and location specific and is correlated with individual learning capabilities

The notion that long-term synaptic plasticity is generated by activity-induced molecular modifications is widely accepted. It is well established that neural cell adhesion molecule (NCAM) is one of the prominent modulators of synaptic plasticity. NCAM can be polysialylated (PSA-NCAM), a reaction that provides it with anti-adhesion properties. In this study we have focused on NCAM and on its polysialylated state, and their relation to learning of an olfactory discrimination task, which depends on both the piriform (olfactory) cortex and hippocampus. We trained rats to distinguish between pairs of odors until rule learning was achieved, a process that normally lasts 6-8 days. At four time points, during training and after training completion, synaptic NCAM and PSA-NCAM expression were assessed in the piriform cortex and hippocampus. We report that NCAM modulation is specific to PSA-NCAM, which is upregulated in the hippocampus one day after training completion. We also report a correlation between the performance of individual rats in an early training stage and their NCAM expression, both in the piriform cortex and hippocampus. Since individual early performance in our odor discrimination task is correlated with the performance throughout the training period, we conclude that early NCAM expression is associated with odor learning capability. We therefore suggest that early synaptic NCAM expression may be one of the factors determining the capability of rats to learn.

Effects of chronic stress on contextual fear conditioning and the hippocampal expression of the neural cell adhesion molecule, its polysialylation, and L1

Chronic stress has been shown to induce time-dependent neurodegeneration in the hippocampus, ranging from a reversible damage to a permanent neuronal loss. This damage has been proposed to impair cognitive function in hippocampus-dependent learning tasks. In this study, we have used a 21-day restraint stress procedure in rats, previously reported to induce reversible atrophy of apical dendrites of CA3 pyramidal cells, to assess whether it may influence subsequent performance in the contextual fear conditioning task under experimental conditions involving high stress levels (1 mA shock intensity as the unconditioned stimulus). In addition, we were interested in the study of the possible cellular and molecular mechanisms involved in the reversible phase of neural damage. Cell adhesion molecules of the immunoglobulin superfamily, such as the neural cell adhesion molecule and L1, are cell-surface macromolecules that, through their recognition and adhesion properties, regulate cell-cell interactions and have been reported to play a key role in cognitive functioning. A second aim of this study was to evaluate whether chronic stress would modulate the expression of the neural cell adhesion molecule, its polysialylation, and L1 in the hippocampus. The results showed that chronic stress facilitated subsequent contextual fear conditioning. They also showed that chronically stressed rats displayed reduced hippocampal neural cell adhesion molecule, but increased polysialylated expression as well as a trend towards exhibiting increased L1 expression. In summary, these results support the view that a 21-day chronic stress regimen predisposes individuals to develop enhanced contextual fear conditioning responses. They also indicate that cell adhesion molecules might play a role in the structural remodelling that occurs in the hippocampus as a consequence of chronic stress exposure.

Regulation of hippocampal cell adhesion molecules NCAM and L1 by contextual fear conditioning is dependent upon time and stressor intensity

Cell adhesion molecules (CAMs) of the immunoglobulin superfamily, NCAM and L1, as well as the post-translational addition of alpha-2, 8-linked polysialic acid (PSA) homopolymers to NCAM (PSA-NCAM), have been implicated in the neural mechanisms underlying memory formation. Given that the degree of stress elicited by the training situation is one of the key factors that influence consolidation processes, this study questioned whether training rats under different stressor intensities (0.2, 0.4, or 1 mA shock intensity) in a contextual fear conditioning task might regulate subsequent expression of NCAM, PSA-NCAM and L1 in the hippocampus, as evaluated immediately after testing rats for conditioning at 12 and 24 h after training. Behavioural inhibition (evaluated as a 'freezing' index) at testing and post-testing plasma corticosterone levels were also assessed. The results showed that 12 h post-training, conditioned animals displayed reduced NCAM, but increased L1, expression. At this time point, the group trained at the highest shock intensity (1 mA) also presented decreased PSA-NCAM expression. Analyses performed 24 h post-training indicated that the 1 mA group exhibited increased NCAM and L1 expression, but decreased expression of PSA-NCAM levels. In addition, L1 values that presented a shock intensity-dependent U-shaped pattern were also increased in the group trained at the lowest shock condition (0.2 mA) and remained unchanged in the intermediate shock condition (0.4 mA). Freezing and corticosterone values at both testing times were positively related with shock intensity experienced at training. Therefore, our results show a complex regulation of CAMs of the immunoglobulin superfamily in the hippocampus that depends upon stressor intensity and time factors. In addition, the pattern of CAMs expression found in the 1 mA group (which is the one that shows higher post-training corticosterone levels and develops the stronger and longer-lasting levels of fear conditioning) supports the view that, after a first phase of synaptic de-adherence during consolidation, NCAM and L1 might participate in the stabilization of selected synapses underlying the establishment of long-term memory for contextual fear conditioning, and suggests that glucocorticoids might play a role in the observed regulation of CAMs.

Opposite effects on NCAM expression in the rat frontal cortex induced by acute vs. chronic corticosterone treatments

The temporal pattern of exposure to glucocorticoids has been reported to be a critical factor in determining the outcome of glucocorticoid actions at the brain. In this work, the effects of different regimes of subcutaneous corticosterone administration (acute-single injection-vs. chronic-daily injection for 21 days) on the expression of the neural cell adhesion molecule (NCAM) were evaluated in different rat brain regions (CA1-CA4, dentate gyrus, frontal cortex, striatum, and hypothalamus). The treatments were selected according to previous studies in which we showed biphasic effects of corticosterone on memory formation, with acute corticosterone effects being facilitating and chronic effects being deleterious. In addition, the chronic treatment was shown by others to result in structural alterations at the hippocampus. NCAM was evaluated given its cell-cell recognition and adhesion properties, and the involvement on synaptic stabilisation subserving long-term memory formation. The results showed a biphasic modulation of NCAM levels at the frontal cortex, with acute corticosterone resulting in enhanced NCAM levels at 8 h and 24 h posttraining, and the chronic treatment decreasing its expression. None of the other brain areas examined showed significant changes in NCAM expression with corticosterone treatments, except for the hypothalamus that showed reduced NCAM levels after the chronic corticosterone regime. These results support the view that NCAM regulation at the frontal cortex might be a mechanism by which corticosterone treatments influence memory formation. They also highlight the hypothalamus as a brain area particularly sensitive to NCAM regulation by prolonged exposure to elevated glucocorticoids.

Are there indicators of remyelination in blood or CSF of multiple sclerosis patients?

Knowing the mechanisms and the times of remyelination is not only an intriguing scientific challenge but it has also important consequences on the therapeutic approach to multiple sclerosis (MS). The neural-cell adhesion molecule (N-CAM) shows tempting suggestions about its possible involvement in reparative mechanisms, and, finally, in remyelination. In fact, its levels progressively increase in the cerebrospinal fluid (CSF) of acute MS patients, paralleling the progressive clinical improvement after the attack. Some information is also given about the ciliary neurotrophic factor (CNTF), whose CSF levels were found to be increased in MS patients who were recovering from an acute exacerbation.

Distribution of N-cadherin and NCAM in neurons and endocrine cells of the human embryonic and fetal gastroenteropancreatic system

For the first time, the distribution of N-cadherin and neural cell adhesion molecule (NCAM) as well as some neuropeptides in nerve cells and endocrine cells of the human embryonic and fetal gastroenteropancreatic system has been detected in early stages (from the 6th postovulatory week onwards). Epithelial cells of the stomach and small intestine contained gastrin and somatostatin and the epithelium of the small intestine also bombesin-positive cells. Myenteric ganglionic cells showed both bombesin and VIP and were NCAM- and N-cadherin-positive at all ages studied. Some basally granulated epithelial cells of stomach, duodenum and the upper part of jejunum contained N-cadherin. The number of these cells increased from 6th to 10th postovulatory weeks. Nerve cells and the cytoplasm of individual epithelial cells of pancreatic ducts were immunoreactive for NCAM and N-cadherin. NCAM- and N-cadherin-positive cells also appeared in Langerhans islets (> 10 weeks), mainly in their peripheral part. NCAM- and N-cadherin-positive endocrine cells were less numerous than endocrine cells producing somatostatin, bombesin, and VIP, probably reflecting the features of embryonic/fetal histogenesis of Langerhans islets from epithelial endocrine cells of pancreatic ducts. NCAM and N-cadherin were localized on the surface of endocrine islets cells as well as in the cytoplasm of single islet cells. This suggests the involvement of both membrane and soluble forms of adhesion proteins in embryonic/fetal histogenesis of human pancreatic islets. The early occurrence of N-cadherin (6th postovulatory week) in enteroendocrine cells supports the existence of a common precursor. The expression of NCAM and N-cadherin in nerve cells and endocrine cells of the human fetal gastroenteropancreatic system may indicate the involvement of neuronal adhesion mechanisms in the development of neuro-endocrine complexes of fetal stomach, small intestine and pancreas.

Effect of NCAM-transfection on growth and invasion of a human cancer cell line

A cDNA encoding the human transmembrane 140 kDa isoform of the neural cell adhesion molecule (NCAM) was transfected into the highly invasive MDA-MB-231 human breast cancer cell line. Transfectants with a homogeneous expression of NCAM showed a restricted capacity for penetration of an artificial basement membrane. However, when injected into nude mice, both control and NCAM-expressing cell lines produced equally invasive tumors. Tumors generated from NCAM-transfected cells were heterogeneous, containing NCAM-positive as well as NCAM-negative areas, indicating the existence of host factors capable of modulating NCAM expression in vivo. In nude mice, NCAM-transfected cells developed tumors with longer latency periods and slower growth rates than tumors induced by NCAM-negative control cells, implying that NCAM may be involved not only in adhesive and motile behavior of tumor cells but also in their growth regulation. There was no indication of differences in cell proliferative characteristics between the different NCAM-transfected and the control transfected cells as determined by flow cytometric DNA analysis, suggesting an increased cell loss as the reason for decreased in vivo growth rate of the NCAM-transfected cells. The fact that NCAM expression influences growth regulation attributes a pivotal role to this cell adhesion molecule during ontogenesis and tumor development.

Regional changes in expression of NCAM, GFAP, and S100 in aging rat brain

In aging brain degenerative processes occur. However, the aging brain still have regenerative capacity although diminished compared to young rats. The neural cell adhesion molecule (NCAM) may be involved in neuroplasticity during regenerative events. In this study, the polypeptide composition and amount of NCAM was determined in regions of brain from young, mature and old rats. During adult life, the amount of NCAM decreased in several brain regions whereas in aged rats, NCAM was enhanced in all brain regions examined. The amount of the glial fibrillary acidic protein (GFAP) increased during aging in all brain regions reflecting general gliosis in the aged rat brain. The amount of the neuro- and gliotrophic protein S100 increased from young adult to mature age in all brain regions investigated followed by a decrease during old age. Aged rats were tested in a Morris water maze and a group of rats (20%) with learning impairment was defined. However, no differences in amount of NCAM, GFAP, or S100 were observed between aged rats with and without spatial learning impairment.

Transfection of glioma cells with the neural-cell adhesion molecule NCAM: effect on glioma-cell invasion and growth in vivo

The tumor growth and the invasive capacity of a rat glioma cell line (BT4Cn) were studied after transfection with the human transmembrane 140-kDa isoform of the neural-cell adhesion molecule, NCAM. After s.c. injection, the NCAM-transfected cells showed a slower growth rate than the parent cell line (BT4Cn). Upon intracerebral implantation with BT4Cn cells and different clones of NCAM-transfected cells, all animals developed neurological symptoms within 13-16 days. However, the tumors showed different growth characteristics. The NCAM-transfected BT4Cn cells were localized in the region of the injection site, with a sharply demarcated border between the tumor and brain tissue. In contrast, the parental cell line showed single-cell infiltration and more pronounced destruction of normal brain tissue. Using a 51Cr-release assay, spleen cells from rats transplanted with BT4Cn tumor cells generally showed a lower cytotoxic response than the spleen cells from rats transplanted with the transfected variants of BT4Cn cells, indicating that the transfection procedure in itself mediated an activation of the immune system. The present data suggest that NCAM may influence the malignant behavior of rat glioma cells in vivo.

Transmembrane neural cell-adhesion molecule (NCAM), but not glycosyl-phosphatidylinositol-anchored NCAM, down-regulates secretion of matrix metalloproteinases

During embryogenesis interactions between cells and extracellular matrix play a central role in the modulation of cell motility, growth, and differentiation. Modulation of matrix structure is therefore crucial during development; extracellular matrix ligands, their receptors, extracellular proteinases, and proteinase inhibitors all participate in the construction, maintenance, and remodeling of extracellular matrix by cells. The neural cell-adhesion molecule (NCAM)-negative rat glioma cell line BT4Cn secretes substantial amounts of metalloproteinases, as compared with its NCAM-positive mother cell line BT4C. We have transfected the BT4Cn cell line with cDNAs encoding the human NCAM-B and -C isoforms. We report here that the expression of transmembrane NCAM-B, but not of glycosyl-phosphatidylinositol-linked NCAM-C, induces a down-regulation of 92-kDa gelatinase (matrix metalloproteinase 9) and interstitial collagenase (matrix metalloproteinase 1), indicating that cellular expression of the recognition molecule NCAM regulates the metabolism of the surrounding matrix.

Intact transmembrane isoforms of the neural cell adhesion molecule are released from the plasma membrane

Three soluble neural cell adhesion molecule (NCAM) polypeptide classes of M(r) values 190,000 (NCAM-s1), 135,000 (NCAM-s2) and 115,000-110,000 (NCAM-s3) have been demonstrated in rat brain and cerebrospinal fluid [Krog, Olsen, Dalseg, Roth and Bock (1992) J. Neurochem. 59, 838-847]. NCAM-s3 is known to arise from released glycosylphosphatidylinositol (GPI)-linked NCAM [He, Finne and Goridis (1987) J. Cell. Biol. 105, 2489-2500] as well as from extracellularly cleaved transmembrane NCAM isoforms [Nybroe, Linnemann and Bock (1989) J. Neurochem. 53, 1372-1378]. In this study the origin of NCAM-s1 and NCAM-s2 and the function of soluble NCAM forms were investigated. It was shown that all three soluble forms could be released from brain membranes with M(r) values identical to the three major membrane-associated forms: the large transmembrane 190,000-M(r) form (NCAM-A), the smaller transmembrane 135,000-M(r) form (NCAM-B) and the GPI-anchored 115,000-110,000-M(r) form (NCAM-C). A polyclonal antibody, directed against transmembrane and cytoplasmic epitopes common to NCAM-A and NCAM-B, was shown to react with NCAM-s1 and NCAM-s2. Furthermore, NCAM-B was shown to be shed in a presumably intact soluble form from membranes of cells transfected with this isoform. Thus, NCAM-s1 and NCAM-s2 probably represent intact released transmembrane NCAM-A and NCAM-B. The soluble transmembrane forms are likely to exist in vivo, as NCAM-s1 and NCAM-s2 were readily demonstrated in cerebrospinal fluid. By density-gradient centrifugation it was shown that shed transmembrane NCAM-B was present in fractions of high, as well as low, density, indicating that a fraction of the shed NCAM is associated with minor plasma membrane fragments. Finally, it was shown that isolated soluble NCAM inhibited cell binding to an immobilized NCAM substratum, attributing a pivotal role to soluble NCAM in vivo as a modulator of NCAM-mediated cell behaviour.

Migratory, invasive and metastatic capacity of NCAM transfected rat glioma cells

A cDNA encoding a transmembrane 140 kDa isoform of the neural cell adhesion molecule, NCAM, was transfected into the rat glioma cell line BT4Cn. Transfectants with a homogeneously high expression of NCAM-B showed a decreased capacity for penetration of an artificial basement membrane when compared to cells transfected with expression-vector alone or untransfected cells. However, when injected subcutaneously into nude mice, both NCAM expressing cells and control cells produced invasive tumors. Nude mice injected with NCAM positive cells developed tumors with slower growth rates as compared to those induced by NCAM negative cells. This implies that NCAM may not only be involved in adhesive and motile behaviour of glioma cells, but also in their growth regulation.

CSF and serum brain-specific creatine kinase isoenzyme (CK-BB), neuron-specific enolase (NSE) and neural cell adhesion molecule (NCAM) as prognostic markers for hypoxic brain injury after cardiac arrest in man

Creatine kinase (CK) and its brain-specific isoenzyme (CK-BB), neuron-specific enolase (NSE), neural cell adhesion molecule (NCAM) and the ions sodium, potassium, chloride and calcium were measured both in CSF and serum and inorganic phosphate in CSF in order to assess their prognostic value in total brain ischemia due to cardiac arrest. The samples were collected at 4, 28 and 76 h after resuscitation. Twenty consecutive patients resuscitated from ventricular fibrillation or asystole were included in the study. Nine of the patients recovered consciousness (recovered) but eleven remained comatose (disabled). The follow-up period was 2 years after which only one patient was still alive. The earliest statistically significant differences between neurologically recovered and disabled patient groups were seen in CSF inorganic phosphate (P = 0.030) already at 4 h and CK-BB (P = 0.046) and NSE (P = 0.020) activity at 28 h. Later, at 76 h after the resuscitation CSF NSE differentiated the groups most clearly (P = 0.014). The values were higher in the disabled patients. A negative correlation between CSF parameters and Glasgow Coma scores was also seen at these timepoints. Statistically significant differences between the groups were seen in both CSF and blood pCO2, pO2, base excess (BE) and actual bicarbonate (HCO3-). CSF or serum NCAM has no prognostic value in anoxic-ischemic coma. The results suggest that in CSF CK-BB and NSE are useful prognostic indicators of hypoxic brain injury when measured 28-76 h after cardiac arrest whereas blood samples have no prognostic value.

Age-related changes in expression of the neural cell adhesion molecule in skeletal muscle: a comparative study of newborn, adult and aged rats

Neural cell adhesion molecule (NCAM) is expressed by muscle and involved in muscle-neuron and muscle-muscle cell interactions. The expression in muscle is regulated during myogenesis and by the state of innervation. In aged muscle, both neurogenic and myogenic degenerative processes occur. We here report quantitative and qualitative changes in NCAM protein and mRNA forms during aging in normal rat skeletal muscle. Determination of the amount of NCAM by e.l.i.s.a. showed that the level decreased from perinatal to adult age, followed by a considerable increase in 24-month-old rat muscle. Thus NCAM concentration in aged muscle was sixfold higher than in young adult muscle. In contrast with previous reports, NCAM polypeptides of 200, 145, 125 and 120 kDa were observed by immunoblotting throughout postnatal development and aging, the relative proportions of the individual NCAM polypeptides remaining virtually unchanged at all ages examined. However, changes in the extent of sialylation of NCAM were demonstrated. Even though the relative amounts of the various NCAM polypeptides were unchanged during aging, distinct changes in NCAM mRNA classes were observed. Three NCAM mRNA classes of 6.7, 5.2 and 2.9 kb were present in perinatal and young adult skeletal muscle, whereas only the 5.2 and 2.9 kb mRNA classes could be demonstrated in aged muscle. This indicates that metabolism of the various NCAM polypeptides is individually regulated during aging. Alternative splicing of NCAM mRNA in skeletal muscle was studied by Northern blotting using DNA oligonucleotide probes specifically hybridizing to selected exons or exon combinations. Exon VASE, which has previously been shown to be present in both brain and heart NCAM mRNA, was virtually absent from skeletal muscle at all ages studied. In contrast, the majority of NCAM mRNA in postnatal skeletal muscle was shown to contain extra exons inserted between exons 12 and 13. Of the various possible exon combinations at this splice site, the combinations 12-a-AAG-13 and 12-a-b seemed to be prevalent in postnatal skeletal muscle. No significant change in the relative proportion of these two exon combinations occurred during aging. The observed upregulation of NCAM protein in aged muscle supports the assumption that an increasing proportion of muscle fibres are denervated in aged muscle. Selective upregulation of the 5.2 and 2.9 kb mRNA forms have previously been demonstrated in muscle cell lines and in primary cultures of muscle cells during formation of myotubes in vitro, and this switch in NCAM mRNA classes has been suggested to correlate with myogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of NCAM by growth factors in serum-free myotube cultures

Regulation of the neural cell adhesion molecule (NCAM) was examined in primary cultures of chick skeletal muscle grown in serum-free defined medium. Relative levels of NCAM (per microgram protein) increased 20-30% in myotubes grown on Matrigel, a reconstituted basement membrane preparation, compared to those grown on collagen; total NCAM levels on Matrigel were increased 40-55% due to the additional increase in total protein. A dose dependent increase in relative NCAM levels in myotubes grown on Matrigel in defined medium was observed with the addition of adsorbed horse serum, while relative NCAM levels in myotubes grown on collagen were unaffected by altering the serum concentration. Thus, extracellular matrix molecules and soluble factors exert trophic effects on myotube NCAM expression. Similar developmental changes in the expression of the different molecular size forms of NCAM occurred in myotubes grown on collagen and Matrigel: levels of 150K and 135K Mr forms decreased during development, while 125K remained prominent in older myotubes. Relative NCAM levels were specifically enhanced 11-26% by several factors: nerve growth factor, thyroxine, insulin-like growth factor II, dibutyryl cyclic AMP, veratridine (a sodium ion channel agonist), and nisoldipine (a calcium ion channel agonist). Total protein and overall myotube development in serum-free cultures were enhanced by fetuin, insulin-like growth factor II, acidic fibroblast growth factor, calcitonin gene-related peptide, dibutyryl cyclic AMP, and veratridine. Thus, changes in extracellular matrix, intracellular calcium, and sodium ions, as well as extracellular trophic factors, such as nerve growth factor, thyroxine, and insulin-like growth factor II, may regulate muscle NCAM expression during embryonic development.

Expression of NCAM mRNA and polypeptides in aging rat brain

In aging brain, degenerative as well as compensatory regenerative processes are believed to occur. The neural cell adhesion molecule NCAM is involved in developmental and regenerative processes in the brain. However, the role of NCAM in aging brain has not been characterized. In this study, the expression of NCAM mRNAs and polypeptides was investigated in aging rat brain. The 7.4 and 6.7 kb NCAM mRNAs were selectively downregulated during postnatal development, and the 5.2 and 2.9 kb NCAM mRNAs were upregulated. However, from postnatal day 40 to old age no change in NCAM mRNA classes was observed. The fraction of NCAM mRNA containing the VASE exon increased postnatally but remained stable during adult life. VASE, which is believed to modulate the binding capacity, seemed to be relatively more abundant in the 7.4 and 6.7 kb NCAM mRNAs, encoding transmembrane NCAM forms, than in the 5.2 and 2.9 kb NCAM mRNAs, coding for glycosyl phosphatidylinositol (GPI) linked NCAM. Conversely, insertion of exons a and AAG between exons 12 and 13, a region containing two fibronectin type III repeats, seemed to be more pronounced in 5.2 and 2.9 kb NCAM mRNAs than in the 7.4 and 6.7 kb mRNAs. During postnatal development an increase in the fraction of 6.7 kb NCAM mRNA containing the exons a and AAG was observed. However, during aging the fraction of NCAM mRNAs containing this exon combination seemed constant. At the protein level, NCAM-A was downregulated both during development and aging. No changes were observed during aging in the composition of soluble NCAM forms in the brain, cerebrospinal fluid or blood plasma. The amount of NCAM in rat brain decreased during postnatal development, but remained at a constant level from postnatal day 40 to old age. To conclude, several changes in NCAM expression occur during early postnatal development emphasizing the important role of this molecule in the morphogenetic processes. During aging, a significant selective downregulation of NCAM-A was observed indicating that in general only minor regenerative processes occur in the brain.

Biphasic changes in NCAM level after an NMDA lesion to the hippocampal formation: a quantitative dot-immunobinding assay

With a quantitative dot-immunobinding assay, the time course changes of neuronal cell adhesion molecule (NCAM) concentrations and total tissue content were monitored in the rat hippocampus after a 40 nmol NMDA injection. A biphasic alteration was observed; a decrease occurred at day 3, an increase at day 30. The time course of changes differed from that of the glial fibrillary acidic protein (GFAP), a marker for reactive astroglial cell, but was similar to that for the markers of sprouting neurites, i.e., low (L) and high (H) molecular weight subunits of the neurofilament polypeptides. It is suggested that NCAM is implicated in the onset of neurite sprouting in the hippocampus after an excitotoxic trauma.

Cerebrospinal fluid markers in neurological disorders

Cerebrospinal fluid (CSF) markers are a useful tool for determining disease progression or activity in some neurological disorders which need parameters both for evaluating treatments and investigating pathobiological evolution in research-oriented follow-up. A number of CSF proteins are reviewed with data on biological properties, analytical methods, clinical usefulness of: myelin basic protein, S-100 protein, glial fibrillary acidic protein, neural-cell adhesion molecule, neuron-specific enolase and others.

Myocardial localization and isoforms of neural cell adhesion molecule (N-CAM) in the developing and transplanted human heart

Neural cell adhesion molecule (N-CAM) has been implicated in cellular interactions involved in cardiac morphogenesis and innervation. Immunohistochemical techniques and Western blot analysis were used to determine the localization and isoforms of N-CAM in the developing and extrinsically denervated human heart. Myocardial and conducting cells in the fetal heart (7-24 wk gestation) exhibited sarcolemmal immunoreactivity, the major desialo N-CAM isoforms being 150, 145, 120, 115, and 110 kD. N-CAM expression appeared to be downregulated in the myocardium during adult life, with relatively little sarcolemmal immunoreactivity being detected in normal donor tissues. In contrast to the temporal changes observed in the myocardium, both the developing and mature cardiac innervation displayed N-CAM immunofluorescence staining, localized to neuronal cell bodies, nerve fascicles and fibres. Extrinsically denervated cardiac allografts, obtained 2 d to 91 mo after transplantation, showed extensive sarcolemmal and intercalated disc immunostaining and expression of 125-, 120-, and 115-kD isoforms. Tissues from explanted recipient hearts and atrial appendage samples obtained during coronary bypass graft operations were also examined and displayed varying amounts of N-CAM immunoreactivity. We conclude that the expression of N-CAM immunoreactivity and isoforms in the human heart is developmentally regulated and may be modulated by factors such as cardiac innervation and myocardial hypertrophy.

A developmental study of soluble L1

L1 is a neural cell adhesion molecule expressed by neurons and it is involved in cell interactions during axon elongation and fasciculation. L1 from rat brain consists of a membrane-inserted Mr 200,000 polypeptide from which two polypeptides of Mr 180,000 and Mr 140,000 can be derived. These latter polypeptides appear both as membrane-associated and as soluble molecules. In this report, both total and soluble L1 in rat brain have been quantified by an enzyme-linked immunosorbent assay. The amount of total L1 per gram brain varies with postnatal age showing a peak value at postnatal day 7. The variation in soluble L1 coincides with the changes in total L1. Thus, soluble L1 constitutes ca 2% of total L1 at all ages investigated. The soluble Mr 140,000 and 180,000 L1 polypeptides are also present in cerebrospinal fluid. Studies of membrane L1 catabolism in cultured fetal rat brain neurons show that the half-life of membrane L1 is less than 24 hr. As a part of membrane L1 catabolism, small amounts of soluble L1 polypeptides are released to include cell surroundings.

Heterogeneity of soluble neural cell adhesion molecule

Soluble neural cell adhesion molecule (NCAM) from rat brain neuronal cell culture media consists predominantly of a polypeptide of Mr approximately 115,000. Minor amounts of a polypeptide of Mr approximately 180,000 and two inconsistently appearing components of Mr 160,000 and 145,000 are also observed. The Mr 115,000 component is derived from the neuronal membrane NCAM components NCAM-A of Mr 190,000, NCAM-B of Mr 140,000, or both. Thus, as a part of the catabolism of membrane NCAM-A plus -B, a minor fraction is posttranslationally cleaved and recovered in the media as discernible soluble NCAM polypeptides. The half-life of membrane NCAM-A plus -B is less than 24 h. Astrocyte culture media contains a predominant soluble NCAM component of Mr 120,000 derived from membrane-associated NCAM-C. A close comparison of deglycosylated soluble NCAM from astrocyte and neuronal cultures showed a small but consistent difference in Mr, a result suggesting that different NCAM polypeptides are released from the membrane of neurons and astrocytes. In contrast to the Mr 115,000-120,000 NCAM polypeptides, the Mr 180,000 polypeptide from neuronal culture media does not seem to be derived from membrane-attached NCAM and may therefore represent a secreted NCAM isoform.

Neuronal and glial markers of the central nervous system

This brief review evaluates the expression of cell-specific markers on differentiated neural cells and, where necessary, on their developing precursors. Within these limitations only the commonly used markers are discussed and those deemed unequivocal are only briefly appraised.

The expression of an N-CAM serum fragment is positively correlated with severity of negative features in type II schizophrenia

The expression of a 70-kD serum fragment of the neural cell adhesion molecule (N-CAM) in schizophrenia is described. Schizophrenic patients (n = 40) were found to have statistically significant increases (p less than 0.0001) in serum N-CAM levels when compared to normal individuals (n = 26), and this could not be associated with age or sex. This difference was more marked (p less than 0.0001) between type II schizophrenics (n = 13) and normal individuals (n = 26) than when patients in the overlap group between type I and type II schizophrenia (n = 18) were compared to normal individuals (p less than 0.001). This difference remained significant (p less than 0.01) when overlap patients were compared to those of type II schizophrenia. Furthermore, schizophrenic patients with lower serum N-CAM proved to be better responders to neuroleptic therapy. We suggest that these elevated serum N-CAM levels reflect an increased synaptic turnover rate in this psychotic state.

Expression of membrane antigens in myotonic dystrophy

Muscle biopsies from a series of myotonic dystrophy patients were analysed for expression of the nerve regulated gene products neural cell adhesion molecule (N-CAM) and 5.1H11. All eight biopsy specimens tested strongly expressed N-CAM and 5.1H11 as assessed by indirect immunofluorescence analysis. These results can be compared with those of Renaud et al (Nature, 1986;319:678) that show apamin binding to be a good marker of myotonic dystrophy muscle membranes. We suggest that in myotonic dystrophy a number of nerve regulated membrane markers are precociously expressed by innervated myofibres and that these are likely to be secondary manifestations resulting from an unidentified primary defect.

Characterization of soluble forms of NCAM

Neural cell adhesion molecule (NCAM) has been described as a family of membrane glycoproteins. However, soluble NCAM immunoreactivity has long been recognized. We here show that soluble NCAM is composed of two quantitatively major polypeptides of Mr 180,000 and 115,000 and two minor components of Mr 160,000 and 145,000. Soluble NCAM was immunochemically identical to membrane NCAM, was polysialylated and carried the HNK-1 epitope. It only constituted 0.8% of total NCAM in newborn rat brain. Soluble NCAM appeared in neuronal cell culture medium 15-30 min after the start of synthesis preceding accumulation of membrane-associated NCAM on the cell surface. This indicates that soluble NCAM contains a secreted component.

Cell adhesion molecule N-CAM is expressed by denervated myofibres in Werdnig-Hoffman and Kugelberg-Welander type spinal muscular atrophies

Immunocytochemical analysis utilising antibody to neural cell adhesion molecule (N-CAM) was carried out on skeletal muscle biopsies from patients with childhood spinal muscular atrophy. Children with both Werdnig-Hoffmann and Kugelberg-Welander disease showed positive N-CAM reactivity. There were however differences in the N-CAM expression profiles in these two sets of patients. All myofibres were positive for N-CAM in the Werdnig-Hoffmann patients. This included both the normal sized fibres and the atrophic fibres. In contrast only the atrophic fibres were positive in the Kugelberg-Welander patients. No reactivity was found associated with the large hypertrophic fibres. It is likely that in the Werdnig-Hoffmann patients the positive N-CAM reactivity reflects unstable innervation of myofibres that had been previously innervated. A similar mechanism may operate in the Kugelberg-Welander patients, but the innervation of the hypertrophic fibres is more stable as they are able to repress N-CAM expression. These results contrast with a lack of N-CAM expression found previously on muscle biopsies from adults with denervation disease.

Topography of N-CAM structural and functional determinants. II. Placement of monoclonal antibody epitopes

The accompanying report (Watanabe, M., A. L. Frelinger III, and U. Rutishauser, 1986, J. Cell Biol., 103:1721-1727) describes a set of monoclonal antibodies (mAbs) directed against N-CAM epitopes representing the known major structural and functional domains of the molecule. In this study, we have generated and separated a variety of peptide fragments from N-CAM, and then used their size and reactivity with each antibody to position the antigenic sites along the peptide chain. This epitope map, together with the biological properties of the antibodies and previous studies on N-CAM, have been used to construct a topographical model for the molecule in the cell membrane.

Nerve dependent regulation of neural cell adhesion molecule expression in skeletal muscle

The expression of neural cell adhesion molecule was analysed by indirect immunofluorescence on adult mouse skeletal muscle subjected to a variety of experimental lesions. Adult mouse muscle does not express neural cell adhesion molecule at the sarcolemma. However, following denervation there is a rapid rise in neural cell adhesion molecule levels; this is initially in the cytoplasm of the myofibres but by 18 days there is intense reactivity at the sarcolemma. A nerve crush lesion was used to show that the increase in neural cell adhesion molecule levels following denervation is accompanied by a switch-off of neural cell adhesion molecule expression following reinnervation. Paralysis of skeletal muscle by botulinum toxin injection is sufficient to activate neural cell adhesion molecule expression. As paralysis of skeletal muscle by botulinum toxin is not accompanied by activation of muscle satellite cells or degeneration products of nerve or myelin, it suggests that the observed levels of neural cell adhesion molecule are synthesised by myofibres. As the expression of neural cell adhesion molecule in these lesions parallels the ability of skeletal muscle to accept innervation it is possible that neural cell adhesion molecule acts as a molecular cue at the sarcolemma in regulating synaptogenesis.

Biosynthesis of the neural cell adhesion molecule: characterization of polypeptide C

The biosynthesis of the neural cell adhesion molecule (N-CAM) was studied in primary cultures of rat cerebral glial cells, cerebellar granule neurons, and skeletal muscle cells. The three cell types produced different N-CAM polypeptide patterns. Glial cells synthesized a 135,000 Mr polypeptide B and a 115,000 Mr polypeptide C, whereas neurons expressed a 200,000 Mr polypeptide A as well as polypeptide B. Skeletal muscle cells produced polypeptide B. The polypeptides synthesized by the three cell types were immunochemically identical. The membrane association of polypeptide C was investigated with methods that distinguish peripheral and integral membrane proteins. Polypeptide C was found to be a peripheral membrane protein, whereas polypeptides A and B were integral membrane proteins with cytoplasmic domains of approximately 50,000 and approximately 25,000 Mr, respectively. The affinity of the membrane binding of polypeptide C increased during postnatal development. The posttranslational modifications of polypeptide C were investigated in glial cell cultures, and it was found to be N-linked glycosylated and sulfated.

Expression of cell adhesion molecule, N-CAM, in diseases of adult human skeletal muscle

Antibody to the cell adhesion molecule N-CAM was used for analysis of cryostat sections using indirect immunofluorescence assay of human muscle biopsies from patients with a variety of muscle diseases. Positive staining was restricted to cases where haematoxylin and eosin staining revealed regenerating myofibers. N-CAM reactivity was specifically found associated with such regenerating fibres. No staining was found on normal adult, degenerating or necrotic fibres. In addition, in chronically denervated muscle disease there was no staining of either atrophic fibres or reinnervated fibres that tended to exist in fibre type specific groupings. N-CAM can therefore be regarded as a specific gene product of regenerating myofibres and is an additional marker of these fibres on biopsy of human muscle.

Cell-free synthesis of the D2-cell adhesion molecule: evidence for three primary translation products

The D2-cell adhesion molecule (D2-CAM) is a membrane glycoprotein that is involved in cell-cell adhesion in the nervous system. To study the biosynthesis of D2-CAM we have translated free and membrane-bound polysomes from rat brain in vitro in the rabbit reticulocyte lysate system. D2-CAM was exclusively synthesized on membrane-bound polysomes. The primary translation products of D2-CAM were three polypeptides of apparent molecular weights 187,000, 134,000, and 112,000. No interconversion between these polypeptides was detected. In contrast to previous suggestions, we conclude that all three D2-CAM polypeptides are primary translation products. When translating polysomes from embryonic and postnatal rat brain, we found that the relative amounts of the three polypeptides synthesized varied with age. Their molecular weights, however, were not age-dependent.

Increased synaptic markers in hippocampus of depressed patients

The neuronal adhesion molecule, D2-protein, and the marker for mature synapses, D3-protein, were studied by crossed immunoelectrophoresis in postmortem samples of human brain hippocampus and frontal cortex. The samples were obtained from 6 patients with endogenous depression, 6 patients with Parkinson's disease, and 9 controls without known neurological or psychiatric disorders. Both D2-protein and D3-protein were significantly increased in hippocampus of depressed patients compared to controls (32% and 30%, respectively) and compared to Parkinson's disease patients (31% and 24%, respectively). However, no significant change was observed in frontal cortex. Combined with the previously observed increase in the level of D2-like protein in blood plasma from depressed patients the findings may indicate that, at least in some regions of the brain, synaptic turnover is increased during depression.

Low cerebrospinal fluid concentration of brain-specific protein D2 in patients with normal pressure hydrocephalus

The synaptic membrane glycoprotein D2 was measured in cerebrospinal fluid (CSF) and plasma in 13 patients with normal pressure hydrocephalus (NPH), in 14 patients with primary degenerative dementia of Alzheimer type (PDD), and in 24 patients without evidence of organic nervous disease (controls). Mean CSF D2 concentration was significantly lower in NPH patients: 299 +/- 48 ng/ml (SEM) (P less than 0.001) than in PDD patients: 658 +/- 50 ng/ml (SEM) and in controls 641 +/- 45 ng/ml (SEM). Plasma D2 concentrations were higher in PDD patients compared with those found in controls. Determination of CSF D2 concentrations might be of diagnostic value in discrimination between patients with NPH and PDD patients with enlarged ventricles associated with diffuse brain atrophy.

Quantification of the D2-glycoprotein in amniotic fluid and serum from pregnancies with fetal neural tube defects

D2 is a glycoprotein existing in both membrane-bound and soluble forms. Employing a specific rabbit antibody against purified human brain D2, we developed an enzyme-linked immunosorbent assay (ELISA) for the quantification of D2 and applied it to amniotic fluids from 87 normal and 36 pathological pregnancies. With a cut-off point of 150 ng D2/ml, no false positive D2 values were obtained in any of the amniotic fluids from normal fetuses, although the alpha-fetoprotein concentrations were slightly increased in 13 cases. No false negative D2 values were found in any of the 18 investigated amniotic fluids from fetuses with anencephaly. Of 8 amniotic fluids from fetuses with spina bifida, 2 false negative D2 values were found. No false negative alpha-fetoprotein values were found in any of the cases with neural tube defects in this study. In 10 amniotic fluids from fetuses with other malformations, 5 samples showed raised D2 concentrations. The D2 level in sera from 10 women carrying normal fetuses and 16 women carrying malformed fetuses was also determined, but no statistically significant difference in D2 level was found in the pathological sera when compared with normal sera. It was concluded that the determination of D2 concentrations in amniotic fluid by means of the D2-ELISA may be used as an additional test in the screening of fetal malformations in early pregnancy.

Immunocytochemical demonstration of the 'neuronal membrane marker' the D2-glycoprotein in human embryos

The regional distribution and cellular localization of the D2-glycoprotein in human embryonic tissues have been investigated by immunocytochemistry at the light microscope level in sections of human embryonic brain, spinal cord, some neural crest derivatives, muscle, liver and skin. the majority of neuronal membranes exhibited a positive staining reaction for D2 already in the earliest (15 mm crown-rump length) embryo examined. By 20 mm crown-rump length and later a positive staining associated with membranes of embryonic muscle, bile canaliculi, epithelial cells of the skin and choroid plexus was also observed. The D2 which is immunochemically related to the neuronal cell adhesion molecule (N-CAM), is supposed to be involved in cell adhesion phenomena. We find this suggested function less compatible with demonstrated localization of the D2-glycoprotein.