Characterization, sequence, and replication of a small cryptic plasmid from Selenomonas ruminantium subspecies lactilytica

A 2.5-kb cryptic plasmid, pJDB21, from the gram-negative ruminal anaerobe, Selenomonas ruminantium subspecies lactilytica, was mapped and sequenced. Five open reading frames (ORFs) were predicted and expression of two ORFs was demonstrated. Analysis of the predicted amino acid sequence of the ORF 1 protein indicated approximately 30% homology with the replication protein (rep) common to many gram-positive plasmids, and a highly conserved sequence representing the origin of replication in these plasmids was located upstream of ORF 1. This finding was consistent with a rolling circle form of replication for pJDB21. Transformation of Escherichia coli K-12 UB1636pol Ats with pJDB21 showed that the plasmid replicated independently of DNA polymerase I and produced a single-stranded DNA intermediate. Deletion analyses localized the E. coli replication function to a 1.4-kb sequence that was mapped to the predicted rep gene.

Detection of anti-SSB antibodies in patients with rheumatic diseases

Anti-SSB antibodies were measured by ELISA in patients with various kinds of connective tissue diseases using SSB antigen purified from fresh rabbit thymus. The SSB antigen reacted with anti-SSB standard serum, and the positive rates in SS, SLE, RA, PBS and MCTD were 55.1%, 48.3%, 32.8%, 30.8% and 26.3%, respectively. The titers of anti-SSB antibodies were higher in SS and SLE patients than in other connective tissue disease patients. However, 10% of normal individuals were found to have anti-SSB antibodies with low titers. The anti-SSB antibodies detected were mainly of IgG isotype. Preliminary analysis of clinical data showed no relationship between anti-SSB and systemic involvement in SS.

Sequence and expression of a Drosophila melanogaster cDNA encoding a putative ribosomal protein

An abundant ovarian cDNA from Drosophila melanogaster has been cloned and sequenced. The predicted protein sequence is similar to that of the ribosomal protein 1024 of Dictyostelium discoideum, the 40S ribosomal protein ys11 of Saccharomyces cerevisiae and a 22 kd protein from Trypanosoma brucei. It seems, therefore, that the Drosophila cDNA also encodes a ribosomal protein. Transcripts are found at all stages of the life cycle but are especially abundant in the ovary, suggesting that this mRNA is maternally stored for utilization in embryogenesis to enable the rapid production of ribosomal proteins and assembly of ribosomes.

Distribution of glutamate-like and glutamine-like immunoreactivities in the rat organ of Corti: a light microscopic and semiquantitative electron microscopic analysis with a note on the localization of aspartate

The light- and electron microscopic localization of glutamate and glutamine in the rat organ of Corti was studied by means of antisera raised against the respective amino acids coupled to carrier proteins. The light microscopic analysis was performed in semithin sections treated according to the peroxidase-antiperoxidase procedure. The two amino acids were visualized in the same ultrathin sections by use of postembedding immunocytochemistry with two different gold particle sizes. The distribution of aspartate-like immunoreactivity was also recorded, but only at the light microscopic level. In the hair cells, the level of glutamate-like immunoreactivity was higher than that in supporting cells but lower than that in the presumed glutamatergic terminals of cerebellar parallel and mossy fibres. The latter types of terminal were sampled from ultrathin sections that had been incubated under the same conditions as the cochlear sections. Within the hair cells, gold particles signalling glutamate were enriched on mitochondria but not on clusters of synaptic vesicles. Glutamine-like immunoreactivity was present in hair cells as well as supporting cells. The glutamate/glutamine ratio, expressed as the ratio between the respective gold particle densities, was considerably lower for hair cells compared with the cerebellar excitatory terminals. No consistent difference was found between outer and inner hair cells in relation to the levels and subcellular distribution of glutamate and glutamine immunoreactivities. Aspartate-like immunoreactivity was accumulated in outer hair cells, with some labelling also of border cells and Böttcher cells. While the present study confirmed the presence of glutamate in hair cells and demonstrated that these cells are also endowed with the important glutamate precursor glutamine, it revealed notable differences between hair cells and presumed glutamatergic terminals in the CNS. These could reflect differences in the synthesis and compartmentation of transmitter glutamate. Methodological factors could also contribute. Alternatively, the differences could be interpreted to suggest that the hair cell transmitter is not glutamate, but a similar compound. Aspartate could be a candidate in the case of the outer hair cells.

Synteny mapping in the bovine: genes from human chromosome 5

In an effort to generate a more complete bovine syntenic map of Type I comparative anchor loci, seven homologs to genes found on HSA5 were mapped using a panel of bovine x rodent hybrid somatic cells. Five HSA5 genes, CSF2, RPS14, PDGFRB, FGFA, and CSF1R, were assigned to bovine syntenic group U22 (chromosome 7), while two others, C9 and HGMCR, mapped to U10 and U5, respectively. Previous studies had assigned the HSA5 marker SPARC to bovine syntenic group U22. The mapping of genes spanning the length of HSA5 in cattle and also in mouse permits syntenic comparisons between prototypic genomes of three mammalian orders, providing insight into the evolutionary history of this region of the ancestral mammalian genome.

Synteny mapping in the bovine: genes from human chromosome 4

Genes homologous to those located on human chromosome 4 (HSA4) were mapped in the bovine to determine regions of syntenic conservation among humans, mice, and cattle. Previous studies have shown that two homologs of genes on HSA4, PGM2 and PEPS, are located in bovine syntenic group U15 (chromosome 6). The homologous mouse genes, Pgm-1 and Pep-7, are on MMU5. Using a panel of bovine x hamster hybrid somatic cells, we have assigned homologs of 11 additional HSA4 loci to their respective bovine syntenic groups. D4S43, D4S10, QDPR, IGJ, ADH2, KIT, and IF were assigned to syntenic group U15. This syntenic arrangement is not conserved in the mouse, where D4s43, D4s10, Qdpr, and Igj are on MMU5 while Adh-2 is on MMU3. IL-2, FGB, FGG, and F11, which also reside on MMU3, were assigned to bovine syntenic group U23. These data suggest that breaks and/or fusions of ancestral chromosomes carrying these genes occurred at different places during the evolution of humans, cattle, and mice.

Nitrate use by tobacco cells in response to N-stress and ammonium nutrition

Characterization of NO 3 (-) use by suspension cultured tobacco cells during a culture cycle is needed to take advantage of cell cultures for further study of the biochemical regulation of NO 3 (-) uptake induction and decay processes. Tobacco (Nicotiana tabacum L., cv. Ky14) cells were cultured with media containing different N sources. Cells cultured with a mixture of NO 3 (-) and NH 4 (+) (40 mM NO 3 (-) plus 20 mM NH 4 (+) , in Murashige and Skoog media) initially grew slightly faster but attained the same maximum cell culture density as those cultured with 40 mM NO 3 (-) only. Cells subcultured with N-free media grew at a similar rate for the first 3 d as those cells grown with N, then ceased further growth. The cessation of growth of cells subcultured with N-free media coincided with depletion of cell NO 3 (-) . The NO 3 (-) influx of cells subcultured with N-free media increased eleven-fold and those grown with N increased four- to five-fold before declining. Maximal NO 3 (-) influx rates occurred at the onset of the stationary growth phase for N-stressed cells, while cells grown with N reached maximums prior to the stationary phase of cell growth. Cells grown with a mixture of NO 3 (-) and NH 4 (+) had lower NO 3 (-) reductase (NR) activity and higher cell NO 3 (-) levels than those of cells grown with NO 3 (-) only. The NR activity of cells subcultured with N-free media peaked within 1 d after subculture before declining to a constitutive level when cell NO 3 (-) was depleted. The level of cell NO 3 (-) plays a critical role in the expression of the NO 3 (-) uptake and reduction processes. The transitions in the expression of NO 3 (-) uptake and reduction activities of tobacco cell suspension cultures should prove valuable for further study of the biochemical and molecular basis for the regulation of these processes.

Wheat vegetative nitrogen compositional changes in response to reduced reproductive sink strength

N redistribution patterns and the N composition of vegetative tissues above the peduncle node of wheat (Triticum aestivum L.) plants with altered reproductive sink strength were evaluated to determine the role of vegetative storage proteins in the temporary storage of excess N destined for export. The degree of leaf senescence symptoms (loss of chlorophyll, total N, and ribulose-1,5-bisphosphate carboxylase/oxygenase) were initially reduced, but the complete senescence of vegetative tissues proceeded even for plants completely lacking reproductive sinks. Plants with 50% less sink strength than control plants with intact spikes redistributed vegetative N to the spike almost as effectively as the control plants. Plants without reproductive sinks exported less N from the flag leaf and had flag leaf blades and peduncle tissues with higher soluble protein and alpha-NH(2) amino acid levels than control plants. An abundant accumulation of polypeptides in the soluble protein profiles of vegetative tissues was not evident in plants with reduced sink strength. Storage of amino acids apparently accommodates any excess N accumulated by vegetative tissues during tissue reproductive growth. Any significant role of vegetative storage proteins in the N economy of wheat is unlikely.

T-lymphocyte proliferation: tyrosine kinases in interleukin 2 signal transduction

Interleukin 2 (IL-2)-induced tyrosine phosphorylation appears to play a major role in IL-2-induced cellular proliferation. Several intracellular substrates including the beta chain of the IL-2 receptor complex (IL-2R beta), raf, MAP2 kinase, the regulatory 83 kDa subunit of phosphatidylinositol-3 kinase and S6 kinases are substrates for the IL-2 receptor activated kinase(s). However, none of the identified members of the IL-2 receptor complex exhibits intrinsic tyrosine kinase activity. Therefore, the IL-2R complex must activate intracellular tyrosine kinases. We have demonstrated that specific tyrosine and serine/threonine kinases are coprecipitated with IL-2 receptor constructs that mediate IL-2-induced cell proliferation but not with those that do not. The IL-2-activated tyrosine kinase appears to be associated with a serine and proline rich intracellular domain which is highly conserved between IL-2R beta and the erythropoietin receptor. Although the responsible kinase has not been identified, lck, fyn, fgr, ltk, hck and lyn can be ruled out as obligatory mediators. Using methods to clone tyrosine kinases from T cells, we have identified potential candidate kinases, including several which had not been known to be expressed by T lymphocytes as well as several unique kinases which had not been previously identified in any cell type.

Genomic organization of the putative human homeobox proto-oncogene HOX-11 (TCL-3) and its endogenous expression in T cells

The HOX-11 (TCL-3) gene, which is abnormally expressed in the leukemic cells of some patients with T-cell acute lymphoblastic leukemia, is a new member of the homeobox gene family. It is structurally altered by the t(10;14) chromosomal translocation, resulting in head-to-tail juxtaposition of HOX-11 with the T-cell receptor delta-chain gene. In order to understand the normal functions of HOX-11 and its role in T-cell leukemia, we have determined the exon-intron structure of the HOX-11 gene. By using oligonucleotide primers flanking an intron of the HOX-11 gene, we have developed a quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay for the expression of HOX-11. We detected HOX-11 expression in multiple cell lineages including normal T cells and two T-cell lines in which the HOX-11 gene appeared to be unaltered in structure. Our results suggest that deregulation of the endogenous expression of HOX-11 in normal T cells represents an essential step towards the formation of this type of T-cell leukemia.

Angiotensin II receptors in the solitary-vagal area of hypertensive rats

Angiotensin II (Ang II) has been proposed to be an endogenous neuromodulator of the baroreceptor reflex at the level of the brain stem solitary-vagal area. Elevated activity of the brain Ang II system has been implicated in the development and maintenance of hypertension in spontaneously hypertensive rats and deoxycorticosterone acetate-salt hypertensive rats. In the present study, we sought to determine if Ang II receptors in the solitary-vagal area exhibited altered binding kinetics in spontaneously hypertensive rats or deoxycorticosterone-salt hypertensive rats. Ang II receptors were examined by quantitative autoradiographic analysis of iodine-125-labeled [Sar1,Ile8]Ang II binding in the solitary-vagal area in six groups of animals: 1) spontaneously hypertensive rats, 2) normotensive Wistar-Kyoto rats, 3) uninephrectomized rats, 4) uninephrectomized rats with a 1% solution of saline for drinking water, 5) uninephrectomized and deoxycorticosterone-treated rats, and 6) uninephrectomized and deoxycorticosterone-treated rats given a 1% solution of saline for drinking water. Blood pressure was significantly elevated in the spontaneously hypertensive rats and deoxycorticosterone-salt rats relative to control animals. There was a significant decrease in the binding affinity (increased KD) for 125I-[Sar1,Ile8]Ang II and a significant increase in the maximum binding density for 125I-[Sar1,Ile8]Ang II in the solitary-vagal area of spontaneously hypertensive rats relative to Wistar-Kyoto rats. Deoxycorticosterone-salt rats also exhibited significantly higher KD and maximum binding density values compared with controls. These results indicate that Ang II receptor binding is altered in the solitary-vagal area of two different models of experimental hypertension and suggest that these changes could contribute to the expression of the hypertensive state.

Metabolic compartmentation of glutamate and glutamine: Morphological evidence obtained by quantitative immunocytochemistry in rat cerebellum

An electron microscopic, double-labelling immunocytochemical procedure was used to assess the level of fixed glutamate and glutamine in different cell profiles in ultrathin sections of rat cerebellar cortex. The procedure was based on sequential immunolabelling with two rabbit antisera, using gold particles of different sizes as markers and formaldehyde vapour as a means to avoid interference between the two incubations. Model sections containing a series of known concentrations of the respective amino acids (aldehyde--fixed to rat brain protein) were incubated together with the tissue material. These revealed a close to linear relationship between gold particle density and antigen concentration throughout the range of biological relevance. The ratio between the density of the two categories of gold particles was calculated for the individual profile types. This ratio showed a 20-fold variation, with the highest glutamate/glutamine ratios obtained for putative excitatory terminals (terminals of parallel fibres in the outer part of the molecular layer, followed by mossy and climbing fibre boutons) and the lowest for glial cells (Bergmann glia, astrocytes in the granule cell layer, and oligodendrocytes). Granule cell bodies and dendrites, and cell bodies and processes of putative GABAergic cells (Purkinje, basket and Golgi cells) displayed intermediate ratios. The ratios corresponded to millimolar ratios (mM fixed glutamate/mM fixed glutamine) ranging from 4.5 to 0.2, tentatively assessed by adjusting for differences in labelling efficiency of the two antigens. Our results show that the compartmentation of glutamate and glutamine, an issue previously addressed mainly in the test tube, can be studied in morphologically intact preparations at a resolution that matches the complexity of CNS tissue. The data indicate that glutamate is effectively converted to glutamine in all categories of glial cells, and that glutamate synthesis prevails in each of the three types of excitatory terminals in the cerebellar cortex. Terminals of putative GABAergic cells form a distinct low glutamate/low glutamine compartment.

S1 nuclease hypersensitive sites in an oligopurine/oligopyrimidine DNA from the t(10;14) breakpoint cluster region

Recurring chromosomal translocations are frequently seen in cancers, especially in leukemias and lymphomas. The genes affected by these chromosomal translocations appear to play an important role in oncogenesis. The mechanism underlying the formation of chromosomal translocation is a subject under extensive study. In chromosomal translocations involving the Ig and TCR loci, complete heptamer-spacer-nonamer signal motifs are usually present at the break of the Ig and TCR genes, indicating the involvement of V-D-J recombinase(s). On the other hand, in only about 50% of the cases signal motif sequences have been found at the break in the other participating chromosome, suggesting that different mechanisms may be involved in the scission of the corresponding chromosome. Here we report the identification of an oligopurine/oligopyrimidine DNA in the t(10;14) breakpoint cluster region associated with T-cell acute lymphoblastic leukemia. S1 nuclease mapping revealed multiple S1 hypersensitive sites in the oligopurine/oligopyrimidine DNA. These data suggest a role for oligopurine/oligopyrimidine sequences (non-B DNA) in the formation of chromosomal translocation.

Differential cellular distribution of two sulphur-containing amino acids in rat cerebellum. An immunocytochemical investigation using antisera to taurine and homocysteic acid

An antiserum to homocysteic acid was raised in rabbits. Immunogens were prepared by coupling this amino acid to bovine serum albumin by means of glutaraldehyde and paraformaldehyde. When applied to semithin or ultrathin sections of rat cerebellum, the antiserum produced selective labelling of glial cells and processes, including the Bergmann fibers. No enrichment of immunoreactivity was detected in nerve terminals of the major excitatory fiber systems. The distribution of homocysteic acid-like immunoreactivity was very different from that of taurine (another sulphur-containing amino acid), as judged from consecutive semithin sections labelled with a postembedding immunoperoxidase procedure and from ultrathin sections labelled with a postembedding double immunogold procedure. Taurine-like immunoreactivity was concentrated in Purkinje cells and was low in glial elements. Our data suggest that the cerebellum contains a glial pool of homocysteic acid (and/or precursors that may undergo spontaneous oxidation to homocysteic acid) and that this amino acid is unlikely to act as a cerebellar transmitter.

Anti-PPD antibodies in Chinese Behçet's disease

Anti-PPD antibody determinations were carried out by the ELISA method using extracted PPD of tubercle bacillus H37RV as the target antigen. The positive rates of anti-PPD antibodies in patients with active tuberculosis, inactive tuberculosis, Behçet's disease, or non-tubercular disease and in a village population were 97.5%, 77.4%, 48.9%, 33.6% and 13.9%, respectively. Although the average titer of anti-PPD antibodies in Behçet's disease was lower (2.168 +/- 0.854) than that in active tuberculosis (3.126 +/- 1.182), it was about the same as that in inactive tuberculosis (2.336 +/- 1.250). In comparison with the village community population surveyed, the average titer of anti-PPD antibodies in Behçet's disease patients was distinctly higher (P less than 0.001). These results indicate that tuberculosis may be etiologically related to Behçet's disease.

[Management of postoperative arrhythmia after open heart surgery in complex congenital heart disease]

The incidence of postoperative arrhythmia was 35.2% in 264 cases with complex congenital heart diseases underwent open heart surgery between Feb, 1988 and Aug, 1989. Postoperative arrhythmia was closely related to preoperative hematocrit, cardiomegaly, prolonged aortic occlusion, ratio of RV/LV systolic pressure greater than 0.75, hypokalemia and low cardiac output syndrome. Infusion of colloid solution and both potassium and magnesium as well as successful surgery and the preventive administration of antiarrhythmic agent played an important role in the prevention and treatment of postoperative arrhythmia.

[Vimentin and tumor diagnosis]

Vimentin was isolated and purified from the pig eye lens by homogenization, ultracentrifugation, extraction in urea buffer and preparative electrophoresis. It was identified with SDS-PAGE and rabbit anti-vimentin was raised against the purified vimentin. The specificity of anti-vimentin was examined with immunohistochemical technique and double immune diffusion. Results showed that the vimentin antibody possessed good specificity for mesenchyme-derived cells. Tumor tissue sections from 151 cases were stained with anti-vimentin, anti-keratin, anti-desmin, anti-S-100 protein, anti-Factor-FVIII released antigen, and anti-lysozyme. Positive staining was obtained in mesenchyme-derived cells, while the epithelial tumor cells did not react with anti-vimentin. It indicated that vimentin antibody is effective for tumor differential diagnosis in surgical pathology.

Suramin prevents binding of interleukin 2 to its cell surface receptor: a possible mechanism for immunosuppression

Suramin, a polysulfonic naphthalene antihelminthic drug, inhibits proliferation of a variety of T-cell lines in vitro and induces immunosuppression in some human patients and thymic atrophy and splenic depletion in mice. Recent clinical trials indicate that suramin has activity against human tumors, indicating that it will be necessary to understand the mechanism by which suramin induces immunosuppression. The T-cell growth factor, interleukin 2 (IL2), is the major growth factor involved in regulating lymphoid differentiation and proliferation and thus regulates, to a major degree, the magnitude and duration of the immune response. We demonstrate herein that suramin induces a concentration-dependent decrease in binding of 125I-labeled IL2 to its receptor complex on human and murine T-lymphocytes. Binding of 125I-labeled IL2 to both Mr 75,000 and 55,000 IL2 binding molecules was inhibited by suramin. Similar concentrations of suramin were required to inhibit binding of 125I-labeled IL2, IL2-induced tyrosine phosphorylation, and IL2-induced proliferation, suggesting that these processes may be linked. With murine cells, suramin-induced growth inhibition could be overcome completely by increasing the concentration of IL2, suggesting that suramin inhibited growth by competing for the IL2 receptor. With human cells, growth inhibition by suramin could only be partially overcome by increasing the concentration of IL2, suggesting that an additional growth-inhibiting mechanism is present. The ability of suramin to prevent binding of IL2 to its receptor was used to confirm that prolonged interaction of IL2 with its receptor is required to induce cell proliferation. Since IL2 plays a role in lymphocyte proliferation and differentiation, the ability of suramin to inhibit binding of IL2 to its receptor may explain, in part, the in vivo immunosuppressive activities of suramin.

[Treatment of rheumatoid arthritis with low doses of multi-glycosides of Tripterygium wilfordii]

Thirty two cases of rheumatoid arthritis were treated with multi-glycosides of Tripterygium wilfordii (T2) in a dosage of 30 mg daily for 12 weeks. Significant improvements in clinical and laboratory variables were observed. In comparison with the results of routine dose of T2 (60 mg per day) treatment, there was no significant difference to be seen between the two treatment plans. Meanwhile, symptom of rash and slightly alimentary canal lower incidences and milder manifestations of side effects of T2 were found in the patients of low dose group than in that of routine dose group. It is suggested that it is reasonable to choose the dose of 30 mg daily as the routine treatment for rheumatoid arthritis patients.

[Sampling survey of mentally deficient people in Sichuan]

From first April to 15th May 1987, 145,201 people were investigated by using the ways of layer, equal probability and mass sampling. Two thousand three hundred and forty two of them were confirmed to be mentally deficient. The incidence was 16.13%. It was estimated that 1,665,000 people have mental deficiency in Sichuan. The estimated range of reliability of 95% was 1,528,000-1,801,000. One million and three hundred ninety three thousand of them only had mental deficiency, while 272,000 had other organic deficiency. Male:female ratio was 101.4:100. The incidence of 6-14 year-old was 38.14%, which was 3 times higher than that of other age groups. Mild mental deficiency was 16.4 times more than severe mental deficiency. The most common causes were hereditary diseases, encephalitis, malnutrition, cerebral trauma, pregnant diseases, etc. All of the causes belonged to preventable diseases.

Aspartate-like and glutamate-like immunoreactivities in the inferior olive and climbing fibre system: a light microscopic and semiquantitative electron microscopic study in rat and baboon (Papio anubis)

A post-embedding immunogold procedure was used to analyse, in a semiquantitative manner, the distributions of aspartate-like and glutamate-like immunoreactivities in the inferior olive and climbing fibre system in rats and baboons. The neurons in the inferior olive were uniformly labelled for aspartate as well as glutamate, indicating a 100% co-localization of these two amino acids in the cell bodies. The level of glutamate-like immunoreactivity in the climbing fibre terminals was similar to that in the parent cell bodies, as judged by a computer-assisted calculation of gold particle densities. In contrast, the level of aspartate-like immunoreactivity in the climbing fibre terminals was only one-seventh of that of the olivary neurons. No differences were found between the hemispheres and vermis. Nerve terminals in the inferior olive were generally moderately labelled with the aspartate antiserum, as were cell bodies of astrocytes. With a few exceptions, the results obtained in baboons were similar to those in rats. Notably, no evidence was found of an enrichment of aspartate-like immunoreactivity in climbing fibres. The present results do not support previous data suggesting that aspartate is the transmitter of the climbing fibres but indicate that glutamate or another excitatory compound should be considered as candidate for this role. Our findings show that the presence of aspartate-like immunoreactivity in cell bodies is an unreliable indicator of transmitter identity.

Distribution of glutamate-like immunoreactivity in excitatory hippocampal pathways: a semiquantitative electron microscopic study in rats

A semiquantitative electron microscopic immunocytochemical procedure was used to study the cellular and subcellular distribution of glutaraldehyde-fixed glutamate in rat hippocampal formation. Ultrathin plastic-embedded sections were incubated with a primary glutamate antiserum followed by a secondary antibody coupled to colloidal gold particles. A computer-assisted assessment of gold particle densities revealed that the axon terminals of all of the main excitatory pathways in the hippocampus were enriched with glutamate-like immunoreactivity relative to other tissue elements, including the parent cell bodies (granule and pyramidal cells). The different excitatory pathways showed slightly different labelling intensities: boutons in the termination zone of the lateral perforant path were covered by higher gold particle densities than boutons situated in the termination zones of the medial perforant path, the Schaffer collateral/commissural pathway and the hilar associational/commissural pathway. The mossy fibre terminals were significantly less enriched in immunoreactivity than terminals of the lateral perforant path and the Schaffer collateral/commissural pathway. Within the terminals, glutamate-like immunoreactivity was concentrated over synaptic vesicles and mitochondria. Terminals establishing symmetric junctions with cell bodies or dendritic stems displayed low particle densities, as did glial cell processes. These findings support the idea that glutamate is a major excitatory neurotransmitter in hippocampal excitatory synapses. Our observations are also in line with biochemical data pointing to the existence of a considerable neuronal and a smaller glial, metabolic pool of glutamate.