Higher levels of antibodies to the tumour-associated antigen cyclin B1 in cancer-free individuals than in patients with breast cancer.

Cyclin B1 is a checkpoint protein that regulates cell division from G2 to the M phase. Studies in mice have shown that cyclin B1 vaccine-induced immunity significantly delayed or prevented the spontaneous cancer development later in life. We hypothesized that if these results showing a protective effect of anti-cyclin B1 antibodies could be extrapolated to the human condition, cancer-free individuals should have higher levels of endogenous antibodies than patients with cancers characterized by the over-expression of this tumour-associated antigen. To test this hypothesis, we characterized a large (1739 subjects) number of multi-ethnic patients with breast cancer (which over-expresses cyclin B1) and matched controls for anti-cyclin B1 immunoglobulin (Ig)G antibodies. Multivariate analyses, after adjusting for the covariates, showed that cancer-free individuals had significantly higher levels of naturally occurring IgG antibodies to cyclin B1 than patients with breast cancer (mean ± standard deviation: 148·0 ± 73·6 versus 126·1 ± 67·8 arbitrary units per ml; P < 0·0001). These findings may have important implications for cyclin B1-based immunotherapy against breast cancer and many other cyclin B1-over-expressing malignancies.

Genetic variants of immunoglobulin γ and κ chains influence humoral immunity to the cancer-testis antigen XAGE-1b (GAGED2a) in patients with non-small cell lung cancer.

GM (γ marker) allotypes, genetic variants of immunoglobulin γ chains, have been reported to be associated strongly with susceptibility to lung cancer, but the mechanism(s) underlying this association is not known. One mechanism could involve their contribution to humoral immunity to lung tumour-associated antigens. In this study, we aimed to determine whether particular GM and KM (κ marker) allotypes were associated with antibody responsiveness to XAGE-1b, a highly immunogenic lung tumour-associated cancer-testis antigen. Sera from 89 patients with non-small cell lung cancer (NSCLC) were allotyped for eight GM and two KM determinants and characterized for antibodies to a synthetic XAGE-1b protein. The distribution of various GM phenotypes was significantly different between XAGE-1b antibody-positive and -negative patients (P = 0·023), as well as in the subgroup of XAGE-1b antigen-positive advanced NSCLC (P = 0·007). None of the patients with the GM 1,17 21 phenotype was positive for the XAGE-1b antibody. In patients with antigen-positive advanced disease, the prevalence of GM 1,2,17 21 was significantly higher in the antibody-positive group than in those who lacked the XAGE-1b antibody (P = 0·026). This phenotype also interacted with a particular KM phenotype: subjects with GM 1,2,17 21 and KM 3,3 phenotypes were almost four times (odds ratio = 3·8) as likely to be positive for the XAGE-1b antibody as the subjects who lacked these phenotypes. This is the first report presenting evidence for the involvement of immunoglobulin allotypes in immunity to a cancer-testis antigen, which has important implications for XAGE-1b-based immunotherapeutic interventions in lung adenocarcinoma.

Racially restricted contribution of immunoglobulin Fcγ and Fcγ receptor genotypes to humoral immunity to human epidermal growth factor receptor 2 in breast cancer.

Tumour-associated antigen human epidermal growth factor receptor 2 (HER2) is over-expressed in 25-30% of breast cancer patients and is associated with poor prognosis. Naturally occurring anti-HER2 antibody responses have been described in patients with HER2 over-expressing tumours. There is significant interindividual variability in antibody responsiveness, but the host genetic factors responsible for this variability are poorly understood. The aim of the present investigation was to determine whether immunoglobulin genetic markers [GM (genetic determinants of γ chains)] and Fcγ receptor (FcγR) alleles contribute to the magnitude of natural antibody responsiveness to HER2 in patients with breast cancer. A total of 855 breast cancer patients from Japan and Brazil were genotyped for several GM and FcγR alleles. They were also characterized for immunoglobulin (Ig)G antibodies to HER2. In white subjects (n = 263), GM 23-carriers had higher levels of anti-HER2 antibodies than non-carriers of this allele (p = 0·004). At the GM 5/21 locus, the homozygotes for the GM 5 allele had higher levels of anti-HER2 antibodies than the other two genotypes (P = 0·0067). In black subjects (n = 42), FcγRIIa-histidine/histidine homozygotes and FcγRIIIa-phenylalanine/valine heterozygotes were associated with high antibody responses (P = 0·0071 and 0·0275, respectively). FcγR genotypes in white subjects and GM genotypes in black subjects were not associated with anti-HER2 antibody responses. No significant associations were found in other study groups. These racially restricted contributions of GM and FcγR genotypes to humoral immunity to HER2 have potential implications for immunotherapy of breast cancer.

Evaluating dentin surface treatments for resin-modified glass ionomer restorative materials.

This in vitro study evaluated the effect of six surface treatments on the shear bond strength of three resin-modified glass ionomers (RMGIs) to dentin. Occlusal surfaces of caries-free third molars were reduced to expose only dentin. Surface treatments were smear layer intact (negative control), Cavity Conditioner, EDTA, Ketac Primer, Self Conditioner, and etching with 35% phosphoric acid followed by the application of Optibond Solo Plus. Filtek Z250 composite resin bonded with Optibond Solo Plus served as a positive control. Conditioning agents were used according to the manufacturers' instructions. After surface treatments, Fuji II LC, Riva LC, Ketac Nano, and Filtek Z250 were placed in copper-band matrices 5 mm in diameter and 2 mm in height and were light-cured for 20 seconds. Specimens were stored in 100% humidity for 24 hours, after which they were placed in deionized water for 24 hours at 37°C. They were then tested under shear forces in an Instron Universal Testing Machine at a crosshead speed of 0.5 mm/min. A two-way analysis of variance and Tukey honestly significant difference statistical analyses (p<0.05) indicated significant interaction between RMGIs and conditioning agents. Acid etching followed by Optibond Solo Plus provided highest bond strengths for all three RMGIs, which were not statistically different from the positive control.

Differential inhibition of trastuzumab- and cetuximab-induced cytotoxicity of cancer cells by immunoglobulin G1 expressing different GM allotypes.

Antibody-dependent cell-mediated cytotoxicity (ADCC), which links the innate and the adaptive arms of immunity, is a major host immunosurveillance mechanism against tumours, as well as the leading mechanism underlying the clinical efficacy of therapeutic antibodies such as cetuximab and trastuzumab, which target tumour antigens, human epidermal growth factor receptor (HER)1 and HER2, respectively. Immunoglobulin (Ig)G antibody-mediated ADCC is triggered upon ligation of Fcγ receptor (FcγR) to the Fc region of IgG molecules. It follows that genetic variation in FcγR and Fc could contribute to the differences in the magnitude of ADCC. Genetic variation in FcγR is known to contribute to the differences in the magnitude of ADCC, but the contribution of natural genetic variation in Fc, GM allotypes, in this interaction has hitherto not been investigated. Using an ADCC inhibition assay, we show that IgG1 expressing the GM 3+, 1-, 2- allotypes was equally effective in inhibiting cetuximab- and trastuzumab-mediated ADCC of respective target cells, in the presence of natural killer (NK) cells expressing either valine or phenylalanine allele of FcγRIIIa. In contrast, IgG1 expressing the allelic GM 17+, 1+, 2+ allotypes was significantly more effective in inhibiting the ADCC - mediated by both monoclonal antibodies - when NK cells expressed the valine, rather than the phenylalanine, allele of FcγRIIIa. These findings have important implications for engineering antibodies (with human γ1 constant region) against malignancies characterized by the over-expression of tumour antigens HER1 and HER2 - especially for patients who, because of their FcγRIIIa genotype, are unlikely to benefit from the currently available therapeutics.

Glyceryl triacetate for Canavan disease: a low-dose trial in infants and evaluation of a higher dose for toxicity in the tremor rat model.

Canavan disease (CD) is a fatal dysmyelinating genetic disorder associated with aspartoacylase deficiency, resulting in decreased brain acetate levels and reduced myelin lipid synthesis in the developing brain. Here we tested tolerability of a potent acetate precursor, glyceryl triacetate (GTA), at low doses in two infants diagnosed with CD, aged 8 and 13 months. Much higher doses of GTA were evaluated for toxicity in the tremor rat model of CD. GTA was given orally to the infants for up to 4.5 and 6 months, starting at 25 mg/kg twice daily, doubling the dose weekly until a maximum of 250 mg/kg reached. Wild-type and tremor rat pups were given GTA orally twice daily, initially at a dose of 4.2 g/kg from postnatal days 7 through 14, and at 5.8 g/kg from day 15 through 23, and thereafter in food (7.5%) and water (5%). At the end of the trial (approximately 90 to 120 days) sera and tissues from rats were analysed for changes in blood chemistry and histopathology. GTA treatment caused no detectable toxicity and the patients showed no deterioration in clinical status. In the high-dose animal studies, no significant differences in the mean blood chemistry values occurred between treated and untreated groups, and no lesions indicating toxicity were detectable in any of the tissues examined. Lack of GTA toxicity in two CD patients in low-dose trials, as well as in high-dose animal studies, suggests that higher, effective dose studies in human CD patients are warranted.

Antibodies to human cytomegalovirus protein UL83 in systemic sclerosis.

OBJECTIVE: To determine whether elevated levels of antibodies to HCMV protein UL83 were present in patients with SSc and if their prevalence was associated with major SSc-associated autoantibodies. METHODS: The study population consisted of 253 Caucasian subjects (110 SSc patients and 143 controls). IgG antibodies to UL83 were measured by an enzyme-linked immunosorbent assay (ELISA). Antibodies to centromere and RNA polymerase (RNAP) were determined by indirect immunofluorescence and immnoprecipitation methods, respectively. RESULTS: The mean level of anti-UL83 antibodies in the sera of SSc patients as a whole was significantly higher than that in control subjects (14.75 vs 10.6 units/microl, p = 0.002). Both subgroups of patients contributed to this variation: compared to controls, anti-UL83 antibody levels were higher in diffuse (16.32 vs 10.6 units/microl, p = 0.012) as well as in those with the limited form of the disease (13.95 vs 10.6 units/microl, p = 0.015). Anti-UL83 antibodies were not associated with major SSc associated autoantibodies. CONCLUSION: Humoral immunity to HCMV protein UL83 may be relevant to the etiopathogenesis of scleroderma.

Transcriptional regulation of the rat eIF4E gene in cardiac muscle cells: the role of specific elements in the promoter region.

Eukaryotic initiation factor 4E (eIF4E) binds to the 7-methylguanosine cap of mRNA and facilitates binding of mRNA to the 40 S ribosome, a rate-limiting step in translation initiation. The expression of eIF4E mRNA and protein increases during growth of cardiac muscle cells (cardiocytes) in vitro. To examine transcriptional regulation of the rat eIF4E gene, 2.1 kB of the rat eIF4E promoter region was cloned and the contribution of specific elements in regulating transcription was determined in primary cultures of rat cardiocytes and in a murine C(2)C(12) myoblast cell line. Sequence analysis of the rat eIF4E promoter revealed 80% sequence similarity with human eIF4E. A putative distal E-box was found at -230 bp and a proximal E-box was located at -77 bp upstream of the transcription start site. Consensus AP-1 motifs were found at -839 and -901 bp and designated as the proximal AP-1 site and distal AP-1 site, respectively. Transfection of reporter gene constructs into cardiocytes showed that deletion of the region between -633 and -318 bp produced a 3-fold increase in basal transcription as compared to the 2.1 kB eIF4E promoter construct. Further deletion of the distal E-box region had no effect on transcription as compared with the 2.1 kB promoter, but deletion of both E-boxes eliminated transcriptional activity. Similar results were obtained in C(2)C(12) myoblasts. To further investigate transcriptional regulation, point mutations were made in the 2.1 kB eIF4E promoter. Mutation of either the distal or proximal E-box had minimal effects on activity in either cell type, but mutation of the distal AP-1 site significantly reduced eIF4E promoter activity by 66+/-4% in cardiocytes. In C(2)C(12) myoblasts, mutating the distal AP-1 site reduced activity by 30+/-4% We conclude that both E-boxes are required for maximal basal activity of the eIF4E promoter, and that the distal AP-1 motif may activate transcription.

Isolation and biochemical characterization of peroxisomes from cultured rat glial cells.

Peroxisomes are now recognized to play important cellular functions and its dysfunction leads to a group of neurological disorders. This study reports peroxisomal enzyme activities in cultured glial cells and peroxisomes isolated from cultured oligodendrocytes and C6 glial cells. Peroxisomal enzyme activities were found to be higher in oligodendroglial cells than in astrocytes or mixed glial cells. We also developed a method for the isolation of peroxisomes from glial cells by a combination of differential and density gradient centrifugation techniques. Peroxisomes from oligodendrocytes in nycodenz gradient were isolated at a density of 1.165 g/ml +/- 0.011. Activities of dihydroxyacetone phosphate acyl transferase, beta-oxidation of lignoceric acid and alpha-oxidation of phytanic acid were almost exclusively associated with the distribution of catalase activity (a marker enzyme for peroxisomes) in the gradient. This protocol should be a resource for studies designed to investigate the structure and function of peroxisomes in brain cells.

Inhibitors of protein phosphatase 1 and 2A differentially regulate the expression of inducible nitric-oxide synthase in rat astrocytes and macrophages.

Nitric oxide produced by inducible nitric-oxide synthase (iNOS) in different cells including brain cells in response to proinflammatory cytokines plays an important role in the pathophysiology of stroke and other neurodegenerative diseases. The present study underlines the importance of protein phosphatase (PP) 1 and 2A in the regulation of the differential expression of iNOS in rat primary astrocytes and macrophages. Compounds (calyculin A, microcystin, okadaic acid, and cantharidin) that inhibit PP 1 and 2A were found to stimulate the lipopolysaccharide (LPS)- and cytokine-mediated expression of iNOS and production of NO in rat primary astrocytes and C6 glial cells. However, these inhibitors inhibited the LPS- and cytokine-mediated expression of iNOS and production of NO in rat resident macrophages and RAW 264.7 cells. Similarly, okadaic acid, an inhibitor of PP 1/2A, stimulated the iNOS promoter-derived chloramphenicol acetyltransferase activity in astrocytes and inhibited the iNOS promoter-derived chloramphenicol acetyltransferase activity in macrophages, indicating that okadaic acid also differentially regulates the transcription of the iNOS gene in astrocytes and macrophages. The observed stimulation of the expression of iNOS in astrocytes and the inhibition of the expression of iNOS in macrophages with the inhibition of PP 1/2A activity clearly delineate a novel role of PP 1/2A in the differential regulation of iNOS in rat astrocytes and macrophages. Because the activation of NF-kappaB is necessary for the induction of iNOS and the expression of tumor necrosis factor (TNF)-alpha also depends on the activation of NF-kappaB, we examined the effect of okadaic acid on the LPS-mediated activation of NF-kappaB and production of TNF-alpha in rat primary astrocytes and macrophages. Interestingly, in both cell types, okadaic acid stimulated the LPS-mediated DNA binding as well as transcriptional activity of NF-kappaB and production of TNF-alpha. This study suggests that the stimulation of iNOS expression in astrocytes by inhibitors of PP 1/2A is possibly due to the stimulation of NF-kappaB activation; however, activation of NF-kappaB is not sufficient for the induction of iNOS in macrophages and that apart from NF-kappaB some other signaling pathway(s) sensitive to PP 1 and/or PP 2A is/are possibly involved in the regulation of iNOS in macrophages. This differential induction of iNOS as compared with similar activation of NF-kappaB by inhibitors of PP 1/2A indicates the involvement of different intracellular signaling events for the induction of iNOS in two cell types of the same animal species.

Sphingomyelinase and ceramide stimulate the expression of inducible nitric-oxide synthase in rat primary astrocytes.

The sphingomyelin signal transduction pathway is known to play a role in mediating the action of various cytokines. Here we examined the possible role of the sphingomyelin signaling pathway on lipopolysaccharide (LPS)- and cytokine-mediated production of NO and the expression of inducible nitric-oxide synthase (iNOS). Sphingomyelinase (SMase) treatment of astrocytes increased the cellular levels of ceramide without the induction of NO production. However, incubation of LPS or cytokine-stimulated astrocytes with SMase or by increasing intracellular ceramide by cell-permeable ceramide analogs (C2- or C6-ceramide) or inhibitor of ceramidase (N-oleoyl ethanolamine) led to a time- and dose-dependent increase in the production of NO. This increase in NO production was accompanied by an increase in iNOS activity, iNOS protein, and iNOS mRNA. Similar to astrocytes, SMase or ceramide analogs also stimulated the LPS- and cytokine-mediated expression of iNOS in the C6 glial cell line. Since activation of NF-kappaB is necessary for the induction of iNOS, we examined the effect of SMase and C2-ceramide on the activation of NF-kappaB. Although SMase or C2-ceramide alone was ineffective in activating NF-kappaB, both stimulated the LPS-mediated activation of NF-kappaB in LPS-activated astrocytes. Inhibition of ceramide and LPS-mediated induction of iNOS by antioxidant inhibitors of NF-kappaB (N-acetylcysteine and pyrrolidine dithiocarbamate) suggest that the stimulatory effect of ceramide on the induction of iNOS is due to the stimulation of NF-kappaB activation and that cellular redox plays a role in the activation of NF-kappaB and induction of iNOS. Inhibition of LPS-mediated as well as LPS and ceramide-mediated induction of iNOS and activation of NF-kappaB by PD98059, a specific inhibitor of activation of mitogen-activated protein (MAP) kinase kinase (MEK), and FPT inhibitor II, a selective inhibitor of Ras farnesyl protein transferase, indicate that the Ras-MAP kinase pathway is involved in LPS-ceramide induced activation of NF-kappaB and induction of iNOS, and that ceramide-mediated signaling events probably converge into the LPS-modulated MAP kinase signaling pathway resulting in greater activation of NF-kappaB and iNOS induction. This study illustrates a novel role of the sphingomyelin-ceramide signaling pathway in stimulating the expression of iNOS via LPS- or cytokine-mediated activation of NF-kappaB in astrocytes.

N-acetyl cysteine inhibits induction of no production by endotoxin or cytokine stimulated rat peritoneal macrophages, C6 glial cells and astrocytes.

The present study underscores the importance of N-acetyl cysteine (NAC), a potent antioxidant, in inhibiting the induction of NO production by lipopolysaccharides (LPS) and cytokines in peritoneal macrophages, C6 glial cells and primary astrocytes. LPS, interleukin-1 beta (IL-1beta), interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) alone or in combinations induced the production of NO to different degrees. NAC when added 2 h earlier to the addition of these stimuli potentially blocked the increase in NO production in macrophages, astrocytes and C6 glial cells. The decrease in NO production by NAC was accompanied by a decrease in inducible nitric oxide synthase (iNOS) activity, in iNOS protein detected by immunoblot analysis with antibodies against iNOS, and in iNOS mRNA determined by reverse-transcriptase coupled polymerase chain reaction (RT-PCR). Time course studies show that inhibition was maximum when NAC was added 2 h prior to the addition of LPS and the degree of inhibition decreased progressively with the increase in time interval when NAC was added after the addition of LPS. In addition to NAC, another antioxidant pyrrolidine dithiocarbamate (PDTC) was also found to inhibit the induction of NO production effectively. Since activation of NF-kappaB is necessary for the induction of iNOS, we examined the effect of NAC on the activation of NF-kappaB. Inhibition of LPS-induced activation of NF-kappaB by NAC in rat peritoneal macrophages suggests that the inhibitory effect of NAC on the induction of iNOS is due to the inhibition of NF-kappaB. Besides NO, NAC also blocked the production of TNF-alpha in rat peritoneal macrophages activated with endotoxin. These results suggest that expression of iNOS and TNF-alpha in macrophages do involve oxygen radicals. The importance of these results in relation to controlling various harmful effects of cytokines released by activated macrophages and glial cells is discussed.

Increasing cAMP attenuates induction of inducible nitric-oxide synthase in rat primary astrocytes.

Nitric oxide produced by inducible nitric-oxide synthase (iNOS) in different brain cells in response to various cytokines plays an important role in the pathophysiology of stroke and other neurodegenerative diseases. This study underlines the importance of cAMP in inhibiting the induction of NO production by lipopolysaccharide (LPS) and cytokines in rat primary astrocytes. Compounds (forskolin, 8-bromo-cAMP, and (Sp)-cAMP) that increase cAMP and activate protein kinase A (PKA) were found to inhibit LPS- and cytokine-mediated production of NO as well as the expression of iNOS, whereas compounds (H-89 and (Rp)-cAMP) that decrease cAMP and PKA activity stimulated the production of NO and the expression of iNOS in rat primary astrocytes. Forskolin, but not the inactive analogue 1,9-dideoxyforskolin, inhibited NO production and iNOS expression in a dose-dependent manner in astrocytes. The inhibition of LPS- and/or cytokine-induced NO production in rat C6 glial cells by forskolin suggest that similar to astrocytes, iNOS expression in C6 cells is also regulated by similar mechanisms. In contrast, in rat peritoneal macrophages the cAMP analogues stimulated the LPS- and cytokine-induced production of NO. In vitro, the PKA had no effect on iNOS activity in LPS-treated astrocytes or macrophages, suggesting that PKA modulates the intracellular signaling events associated with the induction of iNOS biogenesis rather than the post-translational modification of iNOS. The compounds which activate PKA activity, blocked the activation of NF-kappabeta in astrocytes but stimulated the activation of NF-kappabeta in macrophages. This differential regulation of NF-kappabeta activation in two different cell types (astrocytes and macrophages) by the same second messenger (cAMP) indicates that intracellular events or pathways in the activation of NF-kappabeta may be different. Moreover, this inhibition of iNOS expression in LPS- and cytokine-treated astrocytes by cAMP may be of therapeutic potential in NO-mediated cytotoxicity in neurodegenerative diseases.

Lovastatin and phenylacetate inhibit the induction of nitric oxide synthase and cytokines in rat primary astrocytes, microglia, and macrophages.

This study explores the role of mevalonate inhibitors in the activation of NF-kbeta and the induction of inducible nitric oxide synthase (iNOS) and cytokines (TNF-alpha, IL-1beta, and IL-6) in rat primary astrocytes, microglia, and macrophages. Lovastatin and sodium phenylacetate (NaPA) were found to inhibit LPS- and cytokine-mediated production of NO and expression of iNOS in rat primary astrocytes; this inhibition was not due to depletion of end products of mevalonate pathway (e.g., cholesterol and ubiquinone). Reversal of the inhibitory effect of lovastatin on LPS-induced iNOS expression by mevalonate and farnesyl pyrophosphate and reversal of the inhibitory effect of NaPA on LPS-induced iNOS expression by farnesyl pyrophosphate, however, suggests a role of farnesylation in the LPS-mediated induction of iNOS. The inhibition of LPS-mediated induction of iNOS by FPT inhibitor II, an inhibitor of Ras farnesyl protein transferase, suggests that farnesylation of p21(ras) or other proteins regulates the induction of iNOS. Inhibition of LPS-mediated activation of NF-kbeta by lovastatin, NaPA, and FPT inhibitor II in astrocytes indicates that the observed inhibition of iNOS expression is mediated via inhibition of NF-kbeta activation. In addition to iNOS, lovastatin and NaPA also inhibited LPS-induced expression of TNF-alpha, IL-1beta, and IL-6 in rat primary astrocytes, microglia, and macrophages. This study delineates a novel role of the mevalonate pathway in controlling the expression of iNOS and different cytokines in rat astrocytes, microglia, and macrophages that may be important in developing therapeutics against cytokine- and NO-mediated neurodegenerative diseases.

Increased quinolinate immunoreactivity in the peripheral blood monocytes/macrophages from SIV-infected monkeys.

Quinolinate (QUIN), a metabolite in the kynurenine pathway of tryptophan degradation and a neurotoxin that is thought to act through the NMDA receptor system, was localized in cultured peripheral blood monocytes/macrophages from SIV-infected monkeys using a recently developed immunohistochemical method. Significant increases in QUIN immunoreactive (IR) cells were detected in all five SIV-infected monkeys examined. Multinucleated giant cells, a hallmark of lentiviral infection, were visible in selected samples. Treatment with the QUIN precursors, tryptophan and kynurenine, increased the number of QUIN-IR cells in both the control and SIV-infected preparations, perhaps by a mass action mechanism. We hypothesize that in SIV-infected monkeys, infiltrating monocytes/macrophages contribute to the high level of brain QUIN and associated neuropathology.

Comparative distribution of N-acetylaspartylglutamate and GAD67 in the cerebellum and precerebellar nuclei of the rat utilizing enhanced carbodiimide fixation and immunohistochemistry.

The most prevalent peptide in the nervous system, N-acetylaspartylglutamate (NAAG), specifically activates N-methyl D-aspartate (NMDA) receptors and a subclass of metabotropic glutamate receptors. One action of this peptide may be to modulate the release of other neurotransmitters, including gamma-aminobutyric acid (GABA). The present study describes the cellular distribution of NAAG, relative to GABA, in the cerebellum and precerebellar nuclei as a foundation for further physiological investigations. Numerous cells of origin for mossy fibers, including many of the larger neurons of the pontine nuclei, lateral reticular nuclei, vestibular nuclei, reticulotegmental nuclei, and spinal grey, were moderately to strongly stained for NAAG. Many NAAG-labeled fibers were clearly visible in the cerebellar peduncles and central white matter. Mossy fibers and mossy endings were among the most prominent NAAG-immunoreactive elements in the cerebellar cortex. Most neurons in the inferior olive were not stained for NAAG, and only sparse, lightly immunoreactive, climbing fiber-like endings could be identified in restricted regions of the cortical molecular layer. Purkinje neurons ranged from nonreactive to moderately positive, with the great majority being unstained. Cerebellar granule cells did not exhibit any NAAG immunoreactivity. A population of neurons in the deep cerebellar nuclei was highly immunoreactive for NAAG. Additionally, many neurons of the red nucleus were intensely stained for NAAG. Comparisons with staining for the 67 kD form of glutamic acid decarboxylase in serial sections revealed complementary distributions, with NAAG in excitatory pathways and cell groups, and glutamic acid decarboxylase in inhibitory systems. These findings suggest a significant functional involvement of NAAG in the excitatory afferent and efferent projection systems and provide an anatomical basis for investigations into the interactions of NAAG and GABA in the cerebellum.

Two forms of the GABAA receptor distinguished by anion-exchange chromatography.

The GABAA receptor complex was solubilized from rat brain membranes in Triton X-100, enriched by 1012-S affinity chromatography, and subjected to DEAE anion-exchange chromatography. Two forms were distinguished by their differential elution during this HPLC with a KCl gradient. They displayed similar [3H]muscimol- and [3H]flunitrazepam-binding characteristics, as well as [3H]flunitrazepam-binding inhibition by CL 218872. Rechromatography of these distinct ionic forms indicated that they were not in dynamic equilibrium during chromatography. Resolution of these two pharmacologically similar populations of GABAA receptor by anion-exchange HPLC suggests that they differ in charge densities, a condition which may reflect differing glycosylation or phosphorylation states of the complex.