Gangliosides as markers for murine lymphocyte subpopulations.

Antibodies to GM1 ganglioside were used to study murine lymphocyte populations. In A, AKR, and BALB/c mice, anti-GM1 reacts with thymocytes and peripheral T cells. This reactivity of anti-GM1, studied by immunofluorescence, is independent of Thy-1 type and appears to be related to the reactivity of cross-reacting antibodies to asialo GM1 and GD1b, rather than GM1 itself. In addition, a subpopulation of lymphocytes reacting with anti-GM1 and anti-immunoglobulin has been found in approximately 26% of the peripheral lymphocytes of C3H mice, nude mice, and nude heterozygotes. This subpopulation is found in small numbers in A, AKR, and BALB/c mice. These studies demonstrate that antibodies to a chemically defined antigen can be used to identify T cells in many strains of mice and may delineate previously unrecognized lymphocyte subpopulations.

Glycolipids of the mouse peritoneal macrophage. Alterations in amount and surface exposure of specific glycolipid species occur in response to inflammation and tumoricidal activation.

We have characterized the major glycolipid constituents of the mouse peritoneal macrophage, and have demonstrated that alterations in the amount and in the accessibility of specific glycolipid species to galactose oxidase/NaB3H4 labeling, an indicator of glycolipid surface exposure, occur in response to inflammation and as a consequence of activation to a tumoricidal state. The key findings are: (a) Asialo GM1, a major neutral glycolipid constituent of all macrophage populations examined, is accessible to galactose oxidase/NaB3H4 labeling on the surface of TG-elicited and BCG-activated macrophages but not on resident macrophages; (b) GM1 is the predominant ganglioside constituent of the mouse macrophage. Resident macrophages contain two distinct GM1 species, as determined by cholera toxin binding, while TG-elicited and BCG-activated macrophages contain an additional GM1 species. Differences in the relative amounts of these GM1 species, as well as in their accessibility to galactose oxidase/NaB3H4 labeling, exist among the macrophage populations. These observations suggest that both a chemical and spatial reorganization of surface glycolipids occurs in response to inflammation and tumoricidal activation.

Peptide growth factor control of olfactory neurogenesis and neuron survival in vitro: roles of EGF and TGF-beta s.

The olfactory epithelium (OE) is unique in the mammalian nervous system as a site of continual neurogenesis. Though many studies have described this process in vivo and olfactory neurogenesis can be demonstrated in vitro, the specific factors that modulate this process have not been defined. Noting the common ectodermal origin and structural similarity between the OE and epidermis, peptide factors known to modulate epidermal differentiation were tested in OE cultures. Our results demonstrate that EGF acts as a mitogen for the basal cells that give rise to olfactory neurons and that transforming growth factor-beta s (TGF-beta s) promote neurogenesis. Using a neutralizing antibody, we show that it is likely that the endogenous neurogenic factor is TGF-beta 2, or a very closely related factor.

Unique proliferation-associated marker expressed on activated and transformed human cells defined by monoclonal antibody.

The expression, tissue distribution, and preliminary characterization of a cell surface molecule, apparently a glycolipid, recognized by a monoclonal antibody, anti-PAA, were described. This antibody (anti-PAA) was produced by the fusion of myeloma cells NS-1 with spleen cells from a BALB/c mouse, which were sensitized with activated human T-cells generated by allogeneic stimulation in mixed-lymphocyte culture (MLC). Resting human peripheral blood T-cells, B-cells, and monocytes demonstrated weak anti-PAA binding. Binding of proliferating T-cells (phytohemagglutinin- and MLC-activated T-cells) and thymocytes to anti-PAA was two to six times greater than that of resting T-cells. A fifteenfold-increased binding was observed with acute lymphocytic leukemia T-cell lines. Epstein-Barr virus-transformed B-cell lines bound anti-PAA up to sixteenfold greater than resting B-cells. Tumor cell lines of various nonlymphoid origins demonstrated marked reactivity with this antibody. Both benign and malignant cells in hyperplastic tissues, of various origins, bound anti-PAA, whereas their normal, nonproliferating counterparts did not. Normal proliferating cells in these tissues, including cells of the placental chorionic villi and trophoblasts, also bound anti-PAA. Of all lymphoid and nonlymphoid cell lines examined, only chronic lymphocytic leukemia (CLL) cells and some cell lines derived from Burkitt's lymphoma showed weak or no binding. This antibody also failed to react with a variety of nonprimate cell lines. Anti-PAA antibody did not immunoprecipitate any protein from lymphoid tumor cell lines to which it demonstrated a quantitatively high degree of binding, nor did protease treatment of these lines decrease antibody binding. Anti-PAA did, however, bind to glycolipids extracted from these cell lines. Binding of this monoclonal antibody to a minor neutral glycolipid, isolated from the erythroleukemia cell line K562, was about sixfold greater than that of any other K562 neutral glycolipid or ganglioside. Anti-PAA demonstrated weak or undetectable binding to purified, predominant, lymphoid cell membrane's neutral glycolipids and gangliosides. The monoclonal antibody anti-PAA appeared, therefore, to recognize a unique, proliferation-associated, neutral glycolipid present on normal as well as on benign and malignant proliferating cells. The antigen appeared to be universally expressed on proliferating cells from all human tissues with the exception of some Burkitt's cell lines and CLL cells. Nonhuman cell lines, except those for closely related primates, did not express PAA.

Semaphorin 3A is required for guidance of olfactory axons in mice.

Semaphorin 3A (Sema3A) is a membrane-associated secreted protein that has chemorepulsive properties for neuropilin-1 (npn-1)- expressing axons. Although mice lacking the Sema3A protein display skeletal abnormalities and heart defects, most axonal projections in the CNS develop normally. We show here that Sema3A is expressed in the lamina propria surrounding the olfactory epithelium (OE) and by ensheathing cells in the nerve layer of the ventral olfactory bulb (OB) throughout development. Subsets of sensory neurons expressing npn-1 are distributed throughout the OE and extend fibers to the developing OB. In wild-type mice, npn-1-positive (npn-1(+)) axons extend to lateral targets in the rostral OB and medial targets in the caudal OB, avoiding regions expressing Sema3A. In Sema3A homozygous mutant mice, many npn-1(+) axons are misrouted into and through the ventral nerve layer, beginning as early as embryonic day 13 and continuing at least until birth. At postnatal day 0, npn-1(+) glomeruli are atypically located in the ventral OB of Sema3A(-/-) mice, indicating that aberrant axon trajectories are not corrected during development and that connections are made in inappropriate target regions. In addition, subsets of OCAM(+) axons that normally project to the ventrolateral OB and some lactosamine-containing glycan(+) axons that normally target the ventral OB are also misrouted in Sema3A mutants. These observations indicate that Sema3A expression by ensheathing cells plays an important role in guiding olfactory axons into specific compartments of the OB.

Deleted in colorectal cancer (DCC) regulates the migration of luteinizing hormone-releasing hormone neurons to the basal forebrain.

Luteinizing hormone-releasing hormone (LHRH) neurons migrate from the vomeronasal organ (VNO) to the forebrain in all mammals studied. In mice, most LHRH neuron migration is dependent on axons that originate in the VNO but bypass the olfactory bulb and project into the basal forebrain. Thus, cues that regulate the trajectories of these vomeronasal axons are candidates for determining the destination of LHRH neurons. Using in situ hybridization techniques, we examined the expression of Deleted in colorectal cancer (DCC), a vertebrate receptor for the guidance molecule netrin-1, during development of the olfactory system. DCC is expressed by cells in the olfactory epithelium (OE) and VNO, and in cells migrating from the OE and VNO from embryonic day 11 (E11) to E14. Some DCC(+) cells on vomeronasal axons in the nose also express LHRH. However, DCC expression is downregulated beginning at E12, so few if any LHRH neurons in the forebrain also express DCC. In rat, DCC is expressed on TAG-1(+) axons that guide migrating LHRH neurons. We therefore examined LHRH neuron migration in DCC(-/-) mice and found that trajectories of the caudal vomeronasal nerve and positions of LHRH neurons are abnormal. Fewer than the normal number of LHRH neurons are found in the basal forebrain, and many LHRH neurons are displaced into the cerebral cortex of DCC(-/-) mice. These results are consistent with the idea that DCC regulates the trajectories of a subset of vomeronasal axons that guide the migration of LHRH neurons. Loss of DCC function results in the migration of many LHRH neurons to inappropriate destinations.

Effects of gamma-aminobutyric acid(A) receptor manipulation on migrating gonadotropin-releasing hormone neurons through the entire migratory route in vivo and in vitro.

GnRH neurons originate in the nasal compartment and migrate along vomeronasal fibers over the cribiform plate to the forebrain. Previously, we found gamma-aminobutyric acid (GABA) present in GnRH neurons during development. To clarify the influence of GABA across the entire GnRH migration route, we examined the effects of muscimol and bicuculline (GABA(A) agonist and antagonist) in vivo and in vitro, maintaining the integrity of the nasal-forebrain connection. For in vivo experiments, mice were administered muscimol, bicuculline, or vehicle on days 10-15 of pregnancy and were killed on embryonic day 15 (E15). For in vitro experiments, 250-microm parasagittal slices of whole heads of E13 mice were incubated with muscimol, bicuculline, or vehicle for 2 days. Muscimol inhibited GnRH cell migration and decreased extension of GnRH fibers. Bicuculline treatment led to a disorganized distribution of GnRH cells in the forebrain and a concomitant dissociation of GnRH cells from fibers of guidance. These results suggest that GABA's influence on GnRH development changes as the cells move out of the nasal compartment and extend processes toward the median eminence.

Expression of gamma-aminobutyric acid and gonadotropin-releasing hormone during neuronal migration through the olfactory system.

Neurons containing the decapeptide GnRH originate in the olfactory placodes and migrate into the central nervous system during fetal development. The neurotransmitter gamma-aminobutyric acid (GABA) has been proposed as a trophic factor and may also influence neuronal migration. Immunocytochemical analyses were conducted in fetal rats, mice, and humans to identify potential developmental relationships between cells containing GABA, and GnRH neurons. Cells containing GABA were found along the nasal portion of the GnRH migration pathway in rats, mice, and humans during development. A peak number of cells containing immunoreactive GABA was observed in the nasal compartment of rats at embryonic day 15. At this time (E15), a majority of GnRH neurons were clustered in the region of the cribriform plate. By postnatal day 1, all GnRH neurons had migrated into the CNS and GABA cells were virtually absent from the nasal compartment. Double-label and confocal analyses of GABA and GnRH in mice and rats demonstrated that some olfactory GABAergic neurons coexpress GnRH. This implies that neurons that transiently express GABA originate in olfactory placodes and migrate into the forebrain. Based on the transient dual-label and adjacent relationships between GABA and GnRH containing cells in the nasal compartment, and other data showing migrational and trophic roles for GABA in development, we suggest that GABA may directly influence GnRH neuronal migration and development.

Complex glycosphingolipids of the pheochromocytoma cell line PC12: enhanced fucosylglycolipid synthesis following nerve growth factor treatment.

The effect of nerve growth factor treatment on the expression of neutral glycosphingolipids and gangliosides was examined in PC12 pheochromocytoma cells grown in spinner culture. These studies show that PC12 cells contain an unusual group of fucose containing neutral glycolipids and gangliosides. The fucose containing neutral glycolipids, which appear to be derivatives of globoside, are very minor components. However, nearly all of the gangliosides in PC12 cells contain fucose. Two minor neutral glycolipids were isolated from these cells, and were identified as fucosylgloboside and galactosylgloboside. Two major gangliosides were also isolated and identified as fucosyl GM2 and fucosyl GD2. Studies using [3H]fucose to examine the synthesis of fucosylglycolipids indicate that nerve growth factor enhances the incorporation of fucose into glycolipids and gangliosides by as much as 80%. These studies show that all of the gangliosides in PC12 cells appear to increase in concentration when the cells are treated with nerve growth factor in spinner culture. However, only the complex fucose containing neutral glycolipids increase in concentration during this same treatment, while the non-fucosylated precursors do not.

Developmental aspect of the gonadotropin-releasing hormone system.

Gonadotropin-releasing hormone (GnRH) regulates the hypothalamo-pituitary-gonadal (HPG) axis in all vertebrates studied. GnRH neurons that regulate the HPG axis are primarily derived from progenitor cells in the nasal compartment (NC) and migrate along olfactory system derived fibers across the cribriform plate to destinations in the forebrain. Across their long and uncommon migratory route many factors are likely important for their successful development. Several classes of molecules are being studied for their potential influences on migration, including those related to cell surface interactions (membrane receptors, adhesion molecules, extracellular matrix (ECM) molecules, etc.) and those related to communication across distances (neurotransmitters, peptides, chemoattractant or repellent molecules). Of the classes of molecules associated with cell surface interactions, glycoconjugates with terminal galactose, are temporally and spatially expressed on olfactory fibers that guide GnRH neurons and may play role(s) in migration. Of the molecules associated with communication across distances, the neurotransmitter gamma-aminobutyric acid (GABA) is associated with the GnRH migration pathway and influences the position and organization of GnRH neurons in vitro and in vivo. Furthermore, galactose-containing glycoconjugates and GABA are associated with GnRH neurons in species ranging from humans to lamprey. In mice and rats, GABA is found transiently within a subpopulation of GnRH neurons as they migrate through the NC. One of the key elements in considering regulators of GnRH neuron migration is the diversity of GnRH synthesizing cells. For example, only subpopulations of GnRH neurons also contain GABA, specific GABA receptors, or select glycoconjugates. Similarly, treatments that influence GnRH neuronal migration may only affect specific subsets and not the entire population. It is likely that we will not be able to characterize the migration of all GnRH neurons by a single factor. By combining molecular inquiries with genetic models, single cell analyses, and an in vitro migration model, we are beginning to decipher one of the most critical events in the establishment of the reproductive axis.

Differences in the plasma membrane glycoproteins of cultured myeloblastoid and promyelocytic human leukemia (HL60) cells.

Since the mechanisms that control synthesis of surface and internal granule membranes are closely-related within the Golgi apparatus, we have compared the plasma membrane proteins and glycolipids of cells of the human promyelocytic line HL-60 with those of its agranular myeloblastoid variant (HL60-D), and of other human myeloid lines (KG-1a, KG-1 and ML-2). Proteolytic degradation by granule enzymes altered the protein profiles unless multiple inhibitors were included in the cell suspension before lysis and during subsequent handling of the extracts. Polyacrylamide gel electrophoretic profiles of the proteins accessible to lactoperoxidase-catalyzed 125I-labeling or to periodate [3H]-borohydride labeling, as well as those of the glycoproteins bound to and eluted from immobilized concanavalin A, showed distinct patterns. The apparent molecular weights of the two major sialylated glycoproteins were larger in cell lines with a greater content of azurophilic granules. Also, the blastic line incorporated less fucose into glycolipid and contained less complex gangliosides and neutral glycolipids than did the parent. These data demonstrate that, within the limits of this culture model, cells capable of cytoplasmic granule production express a different constellation of surface components.

Subsets of olfactory and vomeronasal sensory epithelial cells and axons revealed by monoclonal antibodies to carbohydrate antigens.

Cell surface glycoconjugates are believed to play an important role in cell-cell interactions during development of CNS pathways. In order to identify developmentally regulated glycoconjugates in the nervous system, monoclonal antibodies were raised and selected for reactivity with carbohydrate antigens. Three monoclonal antibodies were identified, each of which reacts with a defined carbohydrate epitope and reveals a unique pattern of immunoreactivity within the olfactory sensory epithelia, vomeronasal and olfactory nerves and their terminal regions in rats. Antibody CC1 reacts with a globoside-like glycolipid which contains a terminal N-acetylgalactosamine residue. CC1-immunoreactivity is present in just the vomeronasal organ, vomeronasal nerve and in the rostral half of the accessory olfactory bulb. Antibody CC2 reacts with a complex glycolipid which contains a branched chain oligosaccharide terminating with alpha-galactose and alpha-fucose. CC2-immunoreactivity is seen throughout the vomeronasal organ, in dorsomedial regions of the olfactory sensory epithelia, in the vomeronasal and olfactory nerves, the accessory olfactory bulb and dorsomedial glomeruli of the main olfactory bulb. Antibody 1B2 reacts with lacto-N-glycosyl ceramides. 1B2-immunoreactivity is highest at the luminal surfaces of receptor cells throughout the vomeronasal organ and in portions of the olfactory sensory epithelia. 1B2 is also expressed on the surface of a subset of receptor cell bodies, their dendrites and the proximal region of their axons in dorsomedial regions of the main olfactory epithelium.

Altered 9-O acetylation of disialogangliosides in cerebellar Purkinje cells of the nervous mutant mouse.

Some gangliosides in the nervous system are developmentally down-regulated, but many other gangliosides continue to be expressed in the adult nervous system. We have previously demonstrated that the 9-O-acetylated gangliosides recognized by a monoclonal antibody, P-path, confer unique compartmentation among Purkinje cell groups in the normal adult cerebellum. We have continued to explore the role of this group of gangliosides in cerebellar organization by investigating the biochemical and cellular expression of this unique epitope in the cerebellum of the mutant mouse, nervous, where postnatally, most Purkinje cells degenerate. Overall ganglioside composition of nervous cerebellum is similar to wild type cerebellum. However, quantitative analysis of gangliosides by TLC-immunostaining shows that the relative concentration of 9-O-acetylated gangliosides varies considerably. In nervous cerebellum, there is more than a three-fold increase in the concentration of 9-O-acetyl disialolactosyl ceramide (GD3), and 9-O-acetyl disialolactoneotetraosyl ceramide (LD1) is decreased to 25% of wild type. In addition, GD3 ganglioside, the immediate precursor of 9-O-acetyl GD3, is detected at 1/3 of the level of wild type cerebellum, and LD1 ganglioside, the precursor of 9-O-acetyl LD1, is virtually absent from nervous cerebellum. Thus, in nervous cerebellum the ratio of 9-O-acetyl GD3 to its disialoganglioside precursor is dramatically increased compared to wild type cerebellum. In accord with the altered expression of 9-O-acetyl gangliosides, immunoelectron microscopy demonstrates a change in the subcellular distribution in mutant Purkinje cells. Instead of being associated with the somatic and dendritic membranes, P-path immunoreactivity is located internally, in the cytoplasm of Purkinje cell bodies and their dendrites. In addition to the changes in the cerebellum, the other regions of the brain decreased in size by about 15% in the nervous mutant. In the ganglioside composition of these regions of nervous brain, 9-O-acetyl GD3 nearly doubled, but 9-O-acetyl LD1 and other gangliosides did not differ. Our findings of significant changes in 9-O-acetylated gangliosides, accompanied by the overall decrease in brain size, suggest that carbohydrate or glycolipid metabolism is abnormal in the nervous mutant mouse brain.

A monoclonal antibody, WCC4, recognizes a developmentally regulated ganglioside containing alpha-galactose and alpha-fucose present in the rat nervous system.

A monoclonal antibody, WCC4, raised against PC12 cells, recognizes a ganglioside which is present in low concentrations in the postnatal rat nervous system. The antigen is also present in the adrenal and kidney, as determined immunohistochemically, but is not detectable in liver or spleen. A neutral glycosphingolipid is also immunoreactive. In the present report, the chemical characterization of this ganglioside, isolated from PC12 cells, and the anatomical distribution of the antigens recognized by the WCC4 antibody are described. By enzymatic cleavage of terminal saccharide moieties, the ganglioside is identified as alpha-galactosyl, (alpha-fucosyl) GM1. The ganglioside increases in concentration postnatally to day 35 (P35) and is present in a slightly diminished concentration in the adult. Immunohistochemical studies revealed that this glycolipid is also present on neuronal cell soma throughout the cerebrum, cerebellum and spinal cord. It is expressed in highest concentration in the molecular layer of the dentate gyrus and is also present in the olfactory bulb, the molecular layer of the hippocampus, the piriform cortex, the olfactory tubercle and the entorhinal cortex. The dentate molecular layer receives most of its innervation from neurons in the entorhinal cortex, and gangliosides are known to have an effect on plasticity following entorhinal cortical lesions. Therefore, the WCC4 antibody should prove to be a useful tool for the study of the role of endogenous gangliosides in this region of the nervous system.

A unique neuronal glycolipid defines rostrocaudal compartmentalization in the accessory olfactory system of rats.

A monoclonal antibody, CC6, reacts with a complex glycolipid whose expression in the rat is restricted to the olfactory system. Structural analysis reveals that the glycolipid contains two alpha-fucose branches; one each at internal and external beta-galactose residues. Immunocytochemistry demonstrates in rat embryos that CC6 glycolipid expression is restricted to a subset of neurons in the vomeronasal organ (VNO) and their corresponding axon projections in the caudal accessory olfactory bulb (AOB). This pattern of expression in the accessory olfactory system is the converse of the pattern revealed by a previously characterized antiglycolipid antibody that reacts with VNO neurons projecting to the rostral AOB. The CC6-reactive glycolipid is also expressed on a subset of neurons in the main olfactory epithelium. Postnatally, axons from these CC6 positive sensory neurons converge to form a limited number of axon bundles running longitudinally through the nerve layer of the main olfactory bulb. These data provide further evidence that groups of vomeronasal and olfactory neurons expressing unique surface molecules project axons that terminate in selected targets in the AOB and OB, respectively.

Differential laminin isoform expression in the developing rat olfactory system.

Members of the laminin family influence mammalian cells in a variety of ways, mediating adhesion, proliferation, migration, and growth of neuronal processes. Specific laminin domains act through a number of cellular interaction sites to mediate these activities. In the developing olfactory system, axons grow from the olfactory epithelium to synaptic sites in the olfactory bulb a matrix rich in laminins and known mediators of laminin-axon interactions include integrins and a galectin-1/glycoconjugate adhesion system. Using biochemistry, immunocytochemistry, and in situ hybridization, we identified alpha 2, alpha 3, beta 1, beta 2 and gamma 1 laminin isoforms in the late embryonic and neonatal rat olfactory system. However, alpha 1-containing laminin could not be detected in association with olfactory neurons. Immunocytochemistry revealed that beta 2 laminin is preferentially expressed in the ventral and lateral nerve layer of the olfactory bulb and in the main olfactory axon tracks, but is undetectable in the accessory system during embryonic and early postnatal development. In contrast, beta 1 and gamma 1 laminins are evenly distributed throughout the olfactory bulb and in both the main and accessory olfactory axon tracks. The differential localization of laminin chains in vivo is likely to have functional significance for the development and maintenance of the olfactory system.

Migration of neurons containing gonadotropin releasing hormone (GnRH) in slices from embryonic nasal compartment and forebrain.

During development, neurons containing gonadotropin-releasing hormone traverse fiber bundles in the nose, cross into the brain, and move through a maze of glial and axonal fibers. To test whether GnRH neurons utilize cues intrinsic to their migration route to traverse the nasal/brain boundary, tissue slices that maintain connections between the forebrain and nasal compartment were prepared from mouse embryos. Cell migration between the nasal and brain compartments was evident based on changes in cell positions after successive days in vitro.

Differential hormonal modulation of brain antigens recognized by the AB-2 monoclonal antibody.

The expression of monoclonal antibody AB-2 immunoreactivity is age- and sex-dependent in radial glia of developing rat hypothalamus and is regulated by prenatal exposure to gonadal steroids. In the present study, several proteins were recognized by AB-2 and were distributed selectively in subcellular fractions from neonatal hypothalamus (HYP), remaining forebrain (FB), and brainstem regions. Immunoblots revealed polypeptide bands in 3 major molecular weight classes: one at approximately 195 kDa in the cytosolic compartment; and two doublets at 220 kDa and 340 kDa in both microsomal and crude mitochondrial membrane fractions. The 220 kDa and 340 kDa doublets were also Triton-insoluble, suggesting a cytoskeletal association. The 195 kDa-AB-2-immunoreactive band was present in both Triton-soluble and insoluble fractions. AB-2 also recognized several acidic glycolipids extracted from postnatal rat brain regions on immunoblots following high performance thin layer chromatography. One of the bands from postnatal rat brain extracts migrated similarly to purified bovine brain sulfatide, which was also immunoreactive with AB-2. AB-2 immunoreactivity with proteins, polar lipids, and sulfatide suggests that the epitope is a carbohydrate present in multiple cellular compartments. AB-2 recognized the same molecular bands in males and females. Testosterone treatment selectively decreased the level of the 195 kDa AB-2-immunoreactive polypeptide. The 195 kDa AB-2-immunoreactive polypeptide possibly acts in radial glia in the determination of sexually dimorphic neurons in the preoptic area/hypothalamus.

The expression of a fucosyl-ganglioside in the molecular layer of the dentate gyrus following entorhinal cortical lesions.

alpha-Galactosyl (alpha-fucosyl) GM1 is a ganglioside present in the outer two-thirds of the molecular layer of the dentate gyrus of the rat. This region is the terminal zone for afferents from the entorhinal cortex. In order to evaluate changes in ganglioside expression in this region following deafferentation, a monoclonal antibody (WCC4) was used to monitor the ganglioside from 3 to 30 days following a lesion to the entorhinal cortex. From 7 to 14 days postlesion, there was a relative decrease in the width of the band of immunohistochemical staining on the ipsilateral (lesioned) as compared with the contralateral (non-lesioned) side. The results of these studies indicate that alpha-galactosyl (alpha-fucosyl) GM1 is likely to be associated with dendritic shafts in the dentate molecular layer.

Gonadotropin-releasing hormone containing neurons and olfactory fibers during development: from lamprey to mammals.

Gonadotropin releasing-hormone (GnRH) regulates the hypothalamo-pituitary-gonadal axis in all vertebrates. The vast majority of GnRH neurons are thought to be derived from progenitor cells in medial olfactory placodes. Several antibodies and lectins that recognize cell surface carbohydrates have been useful for delineating the migratory pathway from the olfactory placodes and vomeronasal organ, through the nasal compartment, and across the cribriform plate into the brain. In rats, alpha-galactosyl-linked glycoconjugates (immunoreactive with the CC2 monoclonal antibody) are expressed on fibers along the GnRH migration pathway and approximately 10% of the GnRH neuronal population. In lamprey, the alpha-galactosyl binding lectin, Grifonia simplicifolia-I (GS-1), identifies cells and fibers of the developing olfactory system. In contrast to the CC2 immunoreactive GnRH neurons in rats, the GS-1 does not label a subpopulation of presumptive GnRH neurons in lamprey. Results from these and other experiments suggest that GnRH neurons in developing lamprey do not originate within the olfactory placode, but rather within proliferative zones of the diencephalon. However, the overlap of olfactory- and GnRH-containing fibers from prolarval stages to metamorphosis, suggest that olfactory stimuli may play a major role in the regulation of GnRH secretion in lamprey throughout life. By contrast, olfactory fibers are directly relevant to the migration of GnRH neurons from the olfactory placodes in mammalian species. Primary interactions between olfactory fibers and GnRH neurons are likely transient in mammals, and so in later life olfactory modulation of GnRH secretion is likely to be indirect.