The goldfish nervus terminalis: a luteinizing hormone-releasing hormone and molluscan cardioexcitatory peptide immunoreactive olfactoretinal pathway

Antisera to two putative neurotransmitters, luteinizing hormone-releasing hormone (LHRH) and molluscan cardioexcitatory tetrapeptide (H-Phe-Met-Arg-Phe-NH2; FMRF-amide), bind specifically to neurites in the inner nuclear and inner plexiform layers of the goldfish retina. Retrograde labeling showed that intraocular axon terminals originate from the nervus terminalis, whose cell bodies are located in the olfactory nerves. Double immunocytochemical and retrograde labeling showed that some terminalis neurons project to the retina; others may project only within the brain. All terminalis neurons having proven retinal projections were both LHRH- and FMRF-amide-immunoreactive. The activity of retinal ganglion cells was recorded with microelectrodes in isolated superfused goldfish retinas. In ON- and OFF-center double-color-opponent cells, micromolar FMRF-amide and salmon brain gonadotropin-releasing factor ( [Trp7, Leu8] LHRH) caused increased spontaneous activity in the dark, loss of light-induced inhibition, and increased incidence of light-entrained pulsatile response. The nervus terminalis is therefore a putatively peptidergic retinopetal projection. Sex-related olfactory stimuli may act through it, thereby modulating the output of ganglion cells responsive to color contrast.

Ontogeny of enkephalin-like immunoreactivity in the rat hippocampus

The postnatal development of leucine5-enkephalin-like immunoreactivity within the hippocampal formation of the rat has been analyzed using immunocytochemical techniques. From the day of birth to postnatal day three, no intrinsic hippocampal elements exhibit immunoreactivity although labeled axons are found within the fimbria, within the alveus, and in the vicinity of the angular bundle. On postnatal day 4, a few immunoreactive hippocampal neurons can be seen in stratum radiatum of the region CA3 and by postnatal day 8, within the hilus, strata pyramidale and oriens of regio superior, and the subiculum. There is a dramatic increase in the incidence of immunoreactive perikarya between postnatal days 8 and 10 in all fields as well as the appearance of labeled neurons in CA1 stratum pyramidale and stratum granulosum of the dentate gyrus. Two days after the first appearance of immunoreactive perikarya, intensely immunoreactive neurons, labeled much more extensively than is ever seen in the adult, are encountered in each subfield of the hippocampus. The spatio-temporal order in both the emergence of perikaryal immunoreactivity and the transient appearance of intensely immunoreactive neurons follows that of neurogenesis, with immunoreactivity developing 12-14 days after the peak period of last cell division for a given hippocampal region. The incidence of immunoreactive perikarya in the dentate gyrus was quantified in rat pups ranging from postnatal days 8 to 19. The appearance of labeled neurons followed the spatio-temporal gradients that have been described for neurogenesis in this region as well. Immunoreactive perikarya emerged in the suprapyramidal stratum granulosum prior to their emergence in the infrapyramidal zone and in the temporal pole of the dentate earlier than in the mid-dorsoventral dentate. The lateral perforant path and mossy fiber axons, seen to exhibit enkephalin-like immunoreactivity in the adult hippocampal formation, differ in their relative maturity at the age immunoreactivity first appears. Immunoreactivity appears as early as postnatal day 4 in the lateral perforant path, an age at which these axons are just growing into their target field while it is not found within the mossy fibers until after postnatal day 10, an age at which mossy fiber bouton elaboration is well advanced and physiologically competent mossy fiber synapses with the regio inferior pyramidal cells have been established. The latter observation indicates that enkephalin is not necessary for synaptic transmission at the mossy fiber synapse.

Carbonic anhydrase activity of human peripheral nerves: a possible histochemical aid to nerve repair

The return of usable function after injury of peripheral nerves depends upon the appropriate regeneration of axons to their end organs. Debridement trimmings of severed nerves harvested during surgery were stained to demonstrate carbonic anhydrase activity. This histochemical method can be accomplished within 3 to 4 hours of receiving the tissue. Nerve fascicles were readily discriminated from one another by the individual staining patterns of their constituent axons. Axoplasmic staining was predominantly a feature of sensory fibers, and myelin staining was characteristic of skeletal motor axons. Carbonic anhydrase histochemistry may provide a means of accurately matching fascicles in cut nerve ends.

Neuronal development in the Drosophila retina: monoclonal antibodies as molecular probes

The compound eye of D. melanogaster is a reiterative pattern of facets, each containing eight photoreceptor cells in a precise arrangement. This pattern is established in the eye imaginal disc during the third larval instar. A wave of morphogenesis sweeps from posterior to anterior across the disc, leaving in its wake organized clusters of photoreceptor cells. We have used monoclonal antibodies to highlight pattern elements that are not readily observable by other techniques. Monoclonal antibodies can be used to identify the molecules associated with particular patterns, providing links between observable structures and the genes. As an example, we present the purification and N-terminal sequence of a glycoprotein antigen specific to photoreceptor cells and their axons.

Immunohistochemical differences between neurofilaments in perikarya, dendrites and axons. Immunofluorescence study with antisera raised to neurofilament polypeptides (200K, 150K, 70K) isolated by anion exchange chromatography

Neurofilament (NF) proteins (70K, 150K and 200K D) were isolated from 2 M urea extracts of bovine spinal cord by anion exchange chromatography. Antisera to the individual NF polypeptides were produced in rabbits and affinity-purified on Sepharose columns prepared with their own antigen. The NF antisera were completely absorbed by their own antigen at protein concentrations that did not decrease the staining when the absorption was conducted with the heterologous NF antigens. Partial absorption (decrease in immunofluorescence titer) occurred at higher concentrations of the heterologous antigens. Cross-reactivity between the polypeptides of the NF triplet could not be detected by double immunodiffusion. The antisera formed immunoprecipitin lines only when reacted with their own antigen. Conversely, cross-reactivity was demonstrated by the immune blotting procedure. Anti-70K stained all three NF polypeptides. Anti-200K and anti-150K stained both 200K and 150K but not 70K, the main reaction being with their own antigen. The antisera were rendered monospecific by adsorption of the common antigenic determinants on Sepharose columns prepared with the heterologous NF antigens. The localization of the NF proteins was studied by immunofluorescence on cryostat sections of rat brain, cerebellum, spinal cord and posterior root ganglia. All NF antisera (anti-70K, anti-150K and anti-200K) stained axons including Purkinje cell baskets with identical pattern. Spinal cord motor neurons, posterior root ganglia neurons and pyramidal neurons in the cerebral cortex stained with anti-70K and anti-200K. No staining of neuronal perikarya and dendrites was observed with anti-150K. Aluminium-induced neurofibrillary tangles in rabbit spinal cord stained with anti-70K and anti-200K. The tangles were not decorated by anti-150K. It is concluded that a marked difference exists in the concentration of 150K depending on the location, i.e., cell body or axon; or, alternatively, that 150K undergoes modification of antigenic sites within the axon so that it may not be recognized immunologically as a component of the neurofilament within perikarya and dendrites.

Enzymatic determination of subpicomole quantities of phospho-L-arginine in nerve cytoplasm

An ultramicro phospho-L-arginine (Arg-P) assay for nanoliter-volume biological samples is described. The assay and method is demonstrated to be reliable and reproducible for the detection of subpicomole quantities of both Arg-P and ATP in serial samples of cytoplasm from a single, isolated giant nerve fiber from the crayfish Procambarus clarkii. The assay for Arg-P is based on the ATP:L-arginine Nw-phosphotransferase (EC 2.7.3.3.)-catalyzed phosphorylation of ADP to ATP. The generated ATP is measured with a standard luciferin-luciferase bioluminescence method. Arg-P and ATP concentrations of pure axoplasmic samples from resting nerve were found to be approximately 13 and 2 mM, respectively. There was no evidence that substances present in the biological sample interfered with the assay. Recovery of added Arg-P and ATP were approximately 100%. Arg-P and ATP concentrations of isolated biological samples were found to be stable for 1 h at room temperature. The techniques described here are useful for the study of energy metabolism in single, isolated giant cells, and could be easily modified for the study of a variety of metabolic intermediates in situ in functioning tissues and organs.

Ultrastructure of catecholamine-containing axons in the intestine of the domestic fowl

Axons in the duodenum, ileum and rectum of the domestic fowl were identified as catecholamine-containing (CA) on the basis of positive reactivity following chromaffin fixation for electron microscopy. CA-axons in association with blood vessels in all regions of the intestine and in non-vascular sites in the small intestine had a 'typical' adrenergic appearance, in that they contained many small granular vesicles (SGV) and variable numbers of large granular vesicles (LGV). In the rectum the non-vascular CA-axon profiles were atypical, in that there were many elongated LGV and few SGV, and the chromaffin reactivity was weak. The nerve profiles in the rectum were dramatically reduced following 6-hydroxydopamine and reserpine treatment and were absent in rectum cultured in the absence of extrinsic ganglia. It was concluded that the profiles, in spite of their low chromaffin reactivity, truely represent CA-axons. The possibility was raised that the atypical morphology and reduced chromaffin reactivity is due to the presence of adrenaline.

Differences in the organization of actin in the growth cones compared with the neurites of cultured neurons from chick embryos

Sensory neurons from chick embryos were cultured on substrata that support neurite growth, and were fixed and prepared for both cytochemical localization of actin and electron microscopic observation of actin filaments in whole-mounted specimens. Samples of cells were treated with the detergent Triton X-100 before, during, or after fixation with glutaraldehyde to determine the organization of actin in simpler preparations of extracted cytoskeletons. Antibodies to actin and a fluorescent derivative of phallacidin bound strongly to the leading margins of growth cones, but in neurites the binding of these markers for actin was very weak. This was true in all cases of Triton X-100 treatment, even when cells were extracted for 4 min before fixation. In whole-mounted cytoskeletons there were bundles and networks of 6-7-nm filaments in leading edges of growth cones but very few 6-7-n filaments were present among the microtubules and neurofilaments in the cytoskeletons of neurites. These filaments, which are prominent in growth cones, were identified as actin because they were stabilized against detergent extraction by the presence of phallacidin or the heavy meromyosin and S1 fragments of myosin. In addition, heavy meromyosin and S1 decorated these filaments as expected for binding to F-actin. Microtubules extended into growth cone margins and terminated within the network of actin filaments and bundles. Interactions between microtubule ends and these actin filaments may account for the frequently observed alignment of microtubules with filopodia at the growth cone margins.

Modification of a rapidly transported protein in regenerating nerve

From 1 to 28 days after frog sciatic nerve damage, dorsal root ganglia were incubated with [35S] methionine, and the labeled, rapidly transported proteins at various points along the nerve were analyzed on two-dimensional gels. The results show a dramatic increase in the labeling of a protein, which we have designated as A25, only after the arrival of the rapidly transported proteins at regenerating nerve tips. This effect is first seen 3 to 5 days after injury. On gels from regenerating nerves, A25 appears as a series of intense spots with an apparent molecular weight of 70,000. A25 is retrogradely transported from the regenerating nerve tip regions. Since labeled A25 increases only after the rapidly transported proteins reach regions of nerve containing regenerating axons, we conclude that it most likely arises from post-translational modification of a transported protein. Various experiments were conducted to rule out alternative sources of A25 labeling at the nerve periphery.

Immunohistochemical application of monoclonal antibodies against myelin basic protein and neurofilament triple protein subunits: advantages over antisera and technical limitations

Four monoclonal antibodies against guinea pig myelin basic protein (MBP), and four against subunits of bovine neurofilament triplet proteins (NF) were produced and their activity determined by enzyme-linked immunosorbant assay. The specificity and cross-reactivity of these eight monoclonal antibodies and one heterologous antiserum against each of the two central nervous system (CNS) antigens were examined in a histological study using the immunoperoxidase, antibody sandwich technique in rat and human brain tissue. Tissue sections were prepared from paraffin-embedded or fresh brain tissue that had been fixed with one of five different fixatives. The resulting immunoperoxidase labeling was then graded for intensity and examined for artifacts. One monoclonal antibody against MBP and one against NF resulted in labeling that was superior to that given by each of the antisera against their respective antigens. Of the five fixatives tested, a mercuric chloride-formalin solution gave the best preservation of these two antigens in rat and human brain tissue. The mercuric chloride-formalin solution was found to be superior to the other fixatives when immersion fixation was used, and was especially optimal when brains were perfused fixed. Three artifacts were encountered among the various antibody-fixative combinations that produced erroneous, but seemingly specific staining of Purkinje cells, neurons and axons, or astrocytes.

Evidence for the concentration of F-actin and myosin in synapses and in the plasmalemmal zone of axons

Fluorescent staining with phalloidin, a specific probe for F-actin, and antibodies to non-muscle myosin from thymus was used to localize actin and myosin in brain neurons of the rat. Phalloidin and anti-myosin displayed a preferential affinity for synaptic formations in the cerebellum, the brain stem, the spinal cord and the retina. The conclusion that F-actin and myosin are concentrated in synaptic terminals was further established by simultaneous staining of isolated rat brain synaptosomes with phalloidin and anti-thymus myosin as well as by the demonstration of a selective affinity of anti-thymus myosin for a 200 000-Mr protein band in gel electrophoretograms of synaptic fractions. Apart from synaptic areas, phalloidin and anti-thymus myosin reacted also, albeit rather weakly, with a narrow circumferential layer located in the area of the plasma membrane of virtually all axons in the white matter and the spinal roots. The spatial coexistence of myosin and actin in brain synapses and axons is of particular interest in view of various dynamic functions that have been proposed for axonal and synaptic actin.

Slowing of the axonal transport of neurofilament proteins during development

We examined age-dependent changes in neurofilament transport in motor axons of the rat sciatic nerve. SDS-PAGE and gel fluorography confirmed that the distribution of labeled neurofilament triplet protein coincides with the major slow component a (SCa) wave in these neurons. The velocity of neurofilament transport was calculated on the basis of the location of the 50th percentile Of radioactivity in this wave 33 days after motor neurons were labeled by the intraspinal administration of [3H]leucine and [3H]lysine. Overall, the velocity fell from 1.95 mm/day at 3 weeks of age to 1.12 mm/day at 20 weeks. Between 3 and 10 weeks, it fell at a 6-fold higher rate (0.096 mm/day/week) than between 10 and 20 weeks (0.016 mm/day/week). We also found a marked change in the shape of the slow component wave during development. It appeared to consist of several overlapping peaks moving at slightly different velocities in animals 10 weeks of age or less as compared to a single slower moving peak at 20 weeks. We propose that the velocity of slow axonal transport reflects the level of maturation of the neuron, and that the presence of several overlapping peaks Of transported radioactivity in the sciatic nerve of younger animals reflects the presence of several populations of motor axons at different stages of development. We also discuss the relationship between changes in the velocity of neurofilament transport and alterations in the composition of the cytoskeleton that occur as the axon grows in caliber during postnatal development.

Immunocytochemical identification of alpha-endorphin-like material in neurones of the brain and corpus cardiacum of the blowfly, Calliphora vomitoria (Diptera)

A group of the 24-26 paraldehyde fuchsin-positive median neurosecretory cells (MNC) in the pars intercerebralis of the brain of the blowfly, Calliphora vomitoria, has shown immunoreactivity towards three different antibodies to alpha-endorphin, a peptide that corresponds to the amino acid sequence present between residues 61 and 76 of the precursor molecule, beta-lipotropin (beta-LPH). The immunoreactive material could be followed in axons within the median bundle, the tract through which neurosecretory material from the MNC is passed down to the corpus cardiacum (CC). The alpha-endorphin-immunoreactive material was observed leaving the CC in the cardiac-recurrent nerve, dorsal to the proventriculus, in the direction of the abdomen. The cells that contain the alpha-endorphin-like material are different from those of the MNC that contain insulin-, pancreatic polypeptide-, and gastrin/CCK-like peptides. This finding demonstrates the considerable complexity and peptidergic nature of the MNC and constitutes further evidence that morphinomimetic-like peptides are present in the nervous system of invertebrates.

Subunit composition specific to axonally transported tubulin

One week after injection of L-[35S]methionine into the dorsal motor nuclei of the guinea-pig, labelled tubulin carried down the vagal nerve by the slow phase of axonal transport was analysed by one- and two-dimensional gel electrophoresis. Transported tubulin showed a much stronger labelling of the beta-subunit. Isoelectric focussing revealed that both alpha- and beta-subunits were composed of several components. Labelled tubulin was isolated from the brain by cycles of polymerisation and depolymerisation after injection of L-[35S]methionine into the lateral ventricle, for comparison with transported tubulin from the vagal nerve. In addition to the two alpha-components and three beta-components detected in both preparations, axonally transported tubulin contained an extra component (TAX) with a molecular weight corresponding to that of beta-tubulin and with the same isoelectric point as alpha-tubulin. The axon-specific component TAX co-polymerised with tubulin isolated from the brain. Upon peptide mapping by limited proteolysis, the peptide pattern generated from TAX was similar to that of the alpha-tubulin. It is concluded that the axonally transported tubulin contains a modified alpha-subunit which is not found in the bulk of brain tubulin.

Further studies on the mitogenic response of cultured Schwann cells to rat CNS axolemma-enriched fractions

Axolemma-enriched fractions isolated from rat CNS stimulated cultured Schwann cells to divide without changing their morphology. Fluorescent activated cell sorter analysis of the axolemma-stimulated cells demonstrated an approximate 3-fold increase in the number of Schwann cells in the S-phase of the cell cycle. This increase correlated well with increases in the number of [3H]thymidine-labeled nuclei observed by light level radioautography. The membrane-bound mitogen was relatively heat-stable, but trypsin-sensitive, and was inactivated both by lipid extraction and sonication. Liver plasma membranes did not increase the mitotic index over that of untreated cells, indicating the axolemma-induced mitosis was not a general response to exogenous membranes. Increasing serum concentrations in the presence of a constant level of axolemma did not change the mitotic index, suggesting that the axolemma did not cause mitosis by removal of an inhibitory factor in serum. Potential mitogens such as gangliosides, myelin basic protein, heparin, an axolemmal lipid extract, and cGMP had no effect on the cultured Schwann cells. The characteristics of the axolemma-related mitogenic factor are discussed relative to other known mitogens for cultured Schwann cells.

Substance P and enkephalin in transected axons of medulla and spinal cord

The accumulation of transported materials in cut axons is demonstrated by the light and electron microscopic immunocytochemical localization of substance P and enkephalin in the caudal medulla and cervical spinal cord of adult rat. Two days following unilateral knife-cuts in the caudal medulla or spinal (C2-C3) levels, substance P and enkephalin-like immunoreactivity (SPLI and ELI) are detected in lesioned axons located rostral and caudal to the transection. Rostrally, SPLI and ELI are detected in the lateral reticular region and ventrolateral fasciculus corresponding to the location of previously identified bulbospinal pathways. Caudally, previously unidentified, propriospinal pathways showing SPLI are detected in the dorsal columns and in the dorsolateral fasciculus. In contrast, ELI is found caudal to the transection only in the reticular region of the medulla. For both peptides, immunoreactivity is present throughout axons containing numerous large, dense core, and small clear vesicles. These results support the concept of both particulate and soluble modes of transport for substance P and enkephalin within axons of the central nervous system.

Immunohistochemical localization of troponin-C in cultured neurons

Our previous immunofluorescence studies on neurons have demonstrated the presence of myosin in regions of neurons which contained actin. To determine if a system similar to the troponin complex of striated muscle is present in neurons, antibody shown to be specific for the calcium-binding component of troponin (troponin-C) was applied to cultures of embryonic chick and rat dorsal root ganglia. Neurites treated with anti-troponin-C exhibited a bright fluorescence. Accompanying non-neuronal cells were less reactive than the neuronal elements. Immunodiffusion and immunofluorescence showed that the anti-troponin-C did not react with calmodulin, whereas homogenates of the ganglia elicited a positive immunochemical reaction with the anti-troponin-C in Ouchterlony tests. Our results suggest that some intra-axonal movements may be generated by the interaction of actin and myosin and controlled in part by a calcium-troponin-C-dependent mechanism.

The distribution of phosphorylation sites among identified proteolytic fragments of mammalian neurofilaments

Neurofilaments were treated with chymotrypsin or with Staphylococcus aureus V8 protease (V8 protease) and the proteolytic fragments in soluble and particulate centrifugal fractions were identified by immune blotting, using antibodies raised against the Mr = 68,000 (P68), 145,000 (P145), and 200,000 (P200) subunits. The data provide further evidence that each of the three subunits has a different disposition within the filament. A Mr = 160,000 fragment of P200, which may correspond to the side arm projections on neurofilaments, was released into solution by chymotrypsin. In contrast, the proteolytic fragments of P68 and P145 were recovered mainly in the particulate centrifugal fraction, indicating that the two subunits are more closely associated with the filament backbone. Proteolytic cleavage studies on neurofilaments that were 32P-labeled in vivo indicated that the phosphorylated domains in P200 and P145 are localized in a restricted segment of each subunit, which occurs between the chymotryptic and V8 protease cleavage sites. No 32P was associated with the bulk of chymotryptic fragments, which are found in the particulate fraction, are about 40,000 daltons in size, and derive from all three neurofilament subunits. Most of the phosphorylation sites in neurofilaments are peripherally located in the projection domain of P200, suggesting that phosphorylation may modulate interactions between neurofilaments and other neuronal components.

Enkephalin-like immunoreactivity in the pedal ganglion of Mytilus edulis (Bivalvia) and its proximity to dopamine-containing structures

The presence of enkephalin-like immunoreactivity in the pedal ganglion of the bivalve mollusc Mytilus edulis has been demonstrated. Enkephalin-like immunoreactivity is highly localized in those intraganglionic regions rich in dopamine-containing structures. In addition, FMRF-NH2-like (Phe-Met-Arg-Phe-HN2) immunoreactivity was found to occur in intraganglionic regions that are devoid of enkephalin-like immunoreactivity. The differential topographic distribution of these peptidergic immunoreactivities suggests involvement in separate functions. By contrast, the closeness of enkephalin-like immunoreactivity to dopamine histofluorescence supports previous data demonstrating biochemical and physiological links between these two systems.

Adipokinetic hormone and AKH-like peptide demonstrated in the corpora cardiaca and nervous system of Locusta migratoria by immunocytochemistry

An antiserum was raised against tyrosine-adipokinetic hormone ([Tyr1]-AKH). In immunohistochemical procedures, it revealed the AKH cells in the glandular lobes of the corpora cardiaca (CC) of Locusta migratoria with high specificity. In addition, an immunologically related peptide was detected in certain neurons of the central nervous system which suggests that this AKH-like peptide may have a neurotransmitter function. The glandular lobes contain immunoreactive AKH cells in all post-embryonic stages, and no essential differences in morphology and distribution of the cells in nymphs and adults were seen. The amount of AKH, stored predominantly in the cell projections, differ widely among cells and individuals. The brain of adults and nymphs contains several small populations of intensely stained neurons. In last-instar and adult specimens, each half contains 10-12 "normal"-sized neurons in the protocerebrum (including the optic lobe) and deutocerebrum, and in addition 15-18 small reactive neurons. Their axons and numerous branchings traverse the neuropile of proto-, deuto-, and tritocerebrum, except for the pedunculate bodies and antennal lobes. Some of the axons run into the storage lobe of the CC; it is unknown if their content is released into the haemolymph. Other axons run into the ganglia of the stomatogastric nervous system and into the circumoesophageal connectives. The suboesophageal ganglion also contains 8 immunoreactive neurons. It is unknown to which extent the immunoreactive substances in glandular and nervous tissue are chemically and physiologically related.

Ultrastructural relationship between monoamine- and TRH-containing axons in the rat median eminence as revealed by combined autoradiography and immunocytochemistry in the same tissue section

The correlation of dopamine (DA)-, noradrenaline (NA)- or serotonin (5HT)-containing neurons and thyrotropin releasing hormone (TRH)-containing neurons in the median eminence of the rat, as well as the coexistence of monoamines (MA) and TRH in the neurons, were examined by subjecting ultrathin sections to a technique that combines MA autoradiography and TRH immunocytochemistry. The distribution and localization of silver grains after 3H-MA injection were examined by application of circle analysis on the autoradiographs. TRH-like immunoreactive nerve terminals containing the immunoreactive dense granular vesicles were found to have an intimate contact with monoaminergic terminals labeled after 3H-DA, 3H-NA or 3H-5HT infusion in the vicinity of the primary portal capillaries in the median eminence. Synapses between TRH-like immunoreactive axons and MA axons labeled with silver grains, however, have not been observed to date. Findings suggesting the coexistence of TRH and MA in the same nerve terminals or the uptake of 3H-MA into TRH-like immunoreactive nerve terminals, where silver grains after 3H-MA injection were concurrently localized in TRH-like immunoreactive nerve terminals, were rarely observed in the median eminence. Percentages of the nerve terminals containing both immunoreactive granular vesicles and silver grains after 3H-MA injection to total nerve terminals labeled after 3H-MA infusion silver grains were equally very low in 3H-DA, 3H-NA or 3H-5HT, amounting to less than 6.1%.

Localization of insulin-like immunoreactivity in the neurons from primary cultures of rat brain

Brains from 1-day-old rats were dissociated with trypsin and the cells were maintained in culture for 3-4 weeks. These primary cultures contained insulin-like immunoreactivity in the limited populations of neurons. Typically, the fluorescent staining pattern observed in the soma was homogeneous and varicosity-like structures were observed on the neurites of the majority of insulin-like immunoreactive neurons. Serum deprivation of brain cell cultures did not reduce immunoreactivity, whereas cycloheximide caused approx. 80% decrease in the number of insulin-like immunoreactive neurons. Incubation of these cultures with [3H]valine resulted in the incorporation of radioactivity into immunoprecipitable insulin. These results suggest that insulin-like immunoreactivity present in the Central Nervous System (CNS) neurons may be synthesized by brain cell cultures.

Axonal polypeptides cross-reactive with antibodies to neurofilament proteins

Antibodies were prepared to mammalian CNS neurofilament proteins (NFPs) and the antibody specificities were compared using a sensitive immunoblotting method. This procedure was used to detect and characterize cross-reactive proteins and their degradation products in neurofilament preparations. NFPs were prepared by axon flotation. Rabbits were immunized with 200,000, 140,000, and 70,000 NFPs (200K, 140K, and 70K) that had been electrophoretically purified by polyacrylamide gel electrophoresis (PAGE). By immunohistofluorescence it was shown that all antisera stained similar filamentous structures in rat cerebellar neurons. By use of a horseradish peroxidase-conjugated indirect antibody procedure, however, differences were detected in the cross-reactivities of the antisera to rat NFPs, separated by PAGE and electrophoretically transferred to nitrocellulose membranes. Each antiserum exhibited strong binding to the homologous NFP and, thus, was suitable for the detection of cross-reactive polypeptides and proteolytic degradation products derived exclusively from the individual NFPs. Anti-200K, anti-140K, or anti-70K was applied to overloaded two-dimensional nitrocellulose blots of NFPs prepared by axon flotation. Each of the three sera detected a group of unique nonoverlapping polypeptides, some of which were identified as NFP degradation products. A different group of polypeptides was cross-reactive with antiserum to purified glial fibrillary acidic protein. The immunostaining of polypeptides on nitrocellulose was far more sensitive for detecting NFP degradation products than was staining polyacrylamide gels with Coomassie blue. Titers for the antisera were two to three orders of magnitude higher with the immunoblotting procedure than with immunohistologic methods. The sensitivity and the specificity of the described methods suggest their usefulness for examining proteolytic cleavage products of NFPs under a variety of conditions.

Kainic acid prevents peroxidase labeling of retinal ganglion cell bodies in the rat: a possible gate in retrograde axonal transport

Kainic acid, a neurotoxic analogue of glutamate, injected into the vitreous body of the eye, interferes with the retrograde transport of the marker enzyme horseradish peroxidase. This interference is expressed by the absence of detectable peroxidase in the cell bodies of the retinal ganglion cells and by the presence of the marker in the intraretinal portions of the optic axons. These results suggest the hypothesis of the existence of some kind of gate at the proximal portion of the axons which would control the entry of retrogradely moving material into the cell body.