New sonographic marker of borderline ovarian tumor: microcystic pattern of papillae and solid components

OBJECTIVE

To describe and evaluate the utility of a new sonographic microcystic pattern, which is typical of borderline ovarian tumor (BOT) papillary projections, solid component(s) and/or septa, as a new ultrasound marker that is capable of distinguishing BOT from other adnexal masses, and to present/obtain histologic confirmation.

METHODS

In this retrospective study, we identified women with a histologic diagnosis of BOT following surgical resection who had undergone preoperative transvaginal ultrasound (TVS) examination. All images were reviewed for presence or absence of thin-walled, fluid-filled cluster(s) of 1-3-mm cystic formations, associated with solid component(s), papillary projections and/or septa. From the same cases, histopathologic slides of each BOT were examined for presence of any of these microcystic features which had been identified on TVS. To confirm that the microcystic TVS pattern is unique to BOTs, we also selected randomly from our ultrasound and surgical database 20 cases of epithelial ovarian cancer and 20 cases of benign cystadenoma, for review by the same pathologists. To confirm the novelty of our findings, we searched PubMed for literature published in the English language between 2010 and 2018 to determine whether the association between microcystic tissue pattern and BOT has been described previously.

RESULTS

Included in the final analysis were 62 patients (67 ovaries) with preoperative TVS and surgically confirmed BOT on pathologic examination. The mean patient age at surgery was 39.8 years. The mean BOT size at TVS was 60.7 mm. Of the 67 BOTs, 47 (70.1%) were serous, 15 (22.4%) were mucinous and five (7.5%) were seromucinous. We observed on TVS a microcystic pattern in the papillary projections, solid component(s) and/or septa in 60 (89.6%) of the 67 BOTs, including 46 (97.9%) of the 47 serous BOTs, 11 (73.3%) of the 15 mucinous BOTs and three (60.0%) of the five seromucinous BOTs. On microscopic evaluation, 60 (89.6%) of the 67 samples had characteristic 1-3-mm fluid-filled cysts similar to those seen on TVS. In seven cases there was a discrepancy between sonographic and histologic observation of a microcystic pattern. The 20 cystadenomas were mostly unilocular and/or multilocular and largely avascular. None of them or the 20 epithelial ovarian malignancies displayed microcystic characteristics, either on TVS or at histology. On review of 23 published articles in the English medical literature, containing 163 sonographic images of BOT, we found that, while all images contained it, there was no description of the microcystic tissue pattern.

CONCLUSION

We report herein a novel sonographic marker of BOT, a 'microcystic pattern' of BOT papillary projections, solid component(s) and/or septa. This was seen in the majority of both serous and mucinous BOT cases. Importantly, based on comparison of sonographic images and histopathology of benign entities and malignancies, the microcystic appearance seems to be unique to BOTs. No similar description has been published previously. Utilization of this new marker should help to identify BOT correctly, discriminating it from ovarian cancer and benign ovarian pathology, and should ensure appropriate clinical and surgical management. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Pubic bone injuries in primiparous women: magnetic resonance imaging in detection and differential diagnosis of structural injury

OBJECTIVE

To evaluate the utility of magnetic resonance imaging (MRI) in diagnosing structural injury in primiparous women at risk for pelvic floor injury.

METHODS

This was an observational study of 77 women who underwent 3T MRI after delivery. Women were operationally defined as high risk (n = 45) for levator ani muscle tears (risk factors: second-stage labor > 150 min or < 30 min, anal sphincter tear, forceps, maternal age > 35 years and birth weight > 4000 g) or low risk (n = 32): vaginally delivered without these risk factors (n = 12); delivered by Cesarean section after second-stage labor > 150 min (n = 14) or delivered by Cesarean section without labor (n = 6). All women were imaged using fluid-sensitive MRI sequences. Two musculoskeletal radiologists reviewed images for bone marrow edema, fracture, pubic symphysis measurements and levator ani tear.

RESULTS

MRI showed pubic bone fractures in 38% of women at high risk for pelvic floor injury and in 13% of women at low risk for pelvic floor injury (χ(2) (3) = 9.27, P = 0.03). Levator ani muscle tears were present in 44% of the high-risk women and in 9% of the low-risk women (χ(2) (3) = 11.57, P = 0.010). Bone marrow edema in the pubic bones was present in 61% of women studied across delivery categories. Complex patterns of injury included combinations of bone marrow edema, fractures, levator ani tears and pubic symphysis injuries. No MRI-documented injuries were present in 18% of women at high risk and 44% at low risk for pelvic floor injury (χ(2) (1) = 6.2, P = 0.013).

CONCLUSIONS

Criteria identifying primiparous women at risk for pelvic floor injury can predict increased risk of bone and soft tissue changes at the pubic symphysis. Fluid-sensitive MRI has utility for differential diagnosis of structural injury in postpartum women.

Stable public goods cooperation and dynamic social interactions in yeast

Despite long-standing theoretical interest in the evolution of cooperation, empirical data on the evolutionary dynamics of cooperative traits remain limited. Here, we investigate the evolutionary dynamics of a simple public goods cooperative trait, invertase secretion, using a long-term selection experiment in Saccharomyces cerevisiae. We show that average investment in cooperation remains essentially constant over a period of hundreds of generations in viscous populations with high relatedness. Average cooperation remains constant despite transient local selection for high and low levels of cooperation that generate dynamic social interactions. Natural populations of yeast show similar variation in social strategies, which is consistent with the existence of similar selective pressures on public goods cooperation in nature.

WNT signaling modulates the diversification of hematopoietic cells

WNT proteins compose a family of secreted signaling molecules that regulate cell fate and behavior. The possible influence of WNTs on hematopoietic cell fate was examined. Both hematopoietic progenitor cell (HPC)-enriched embryonic avian bone marrow cells and the quail mesodermal stem cell line QCE6 were used for these studies. Under optimized conditions, the bone marrow and QCE6 cells behaved identically and developed into red blood cells (RBCs), monocytes, macrophages, granulocytes, and thrombocytes. This broad range of blood cell phenotypes exhibited by QCE6 cells was dependent on their active expression of WNT11. However, when QCE6 cells were prevented from producing WNT11-by expression of a stably transfected WNT11 antisense transgene-the cultures were dominated by highly vacuolated macrophages. RBCs were absent from these cultures, and the presence of monocytes was greatly diminished. Exposure of these WNT11 antisense cells to soluble WNT11 or WNT5a restored the broad range of blood cell phenotypes exhibited by parental QCE6 cells. Overexpression of WNT protein in QCE6 cells further increased the prevalence of RBCs and monocytes and greatly diminished the appearance of macrophages. Accordingly, treatment of HPC-enriched bone marrow cultures with soluble WNT11 or WNT5a inhibited macrophage formation. Instead, monocytes and RBCs were the prevalent cells displayed by WNT-treated bone marrow cultures. Together, these data indicate that WNTs may play a major role in regulating hematopoietic cell fate.

Displaced starburst amacrine cells of the rabbit retina contain the 67-kDa isoform, but not the 65-kDa isoform, of glutamate decarboxylase

The cholinergic identity of retinal starburst amacrine neurons is well established, but recent evidence suggests that these cells are GABAergic as well. Confirmation of this dual transmitter function requires the demonstration of glutamate decarboxylase (GAD), the biosynthetic enzyme for GABA, within starburst cells. The current work was undertaken to determine whether rabbit retinal starburst amacrine neurons contain either of the two known isoforms of GAD. To do this, we have examined the localization of the following: (1) the 65-kDa isoform of GAD; (2) the 67-kDa isoform of GAD; (3) choline acetyltransferase; and (4) the fluorescent dye DAPI, a marker for cholinergic amacrine cells. In addition, we labeled displaced starburst neurons directly, by injecting them with Lucifer Yellow in vitro. Four strata within the inner plexiform layer contained immunoreactive GAD65. A non-GAD65-immunoreactive zone separated the two innermost strata (G3 and G4); this zone contained (1) the dendrites of individual Lucifer Yellow-injected, displaced starburst amacrine cells; (2) dendrites immunoreactive for choline acetyltransferase; and (3) processes of DAPI-labeled amacrine cells. Immunoreactive GAD67 appeared in the same strata that contained GAD65, and in at least two additional strata, one of which lay at precisely the same depth as the proximal cholinergic stratum. In addition, the somas of displaced starburst cells were strongly immunoreactive for GAD67, but not for GAD65. These results demonstrate (1) that displaced starburst amacrine cells contain the 67-kDa isoform of GAD, but not the 65-kDa isoform; and (2) that the dendrites of starburst (67-kDa GAD) amacrines, and the dendrites of 65-kDa-GAD-containing amacrines, occupy different strata within the inner plexiform layer. Thus, displaced starburst cells do contain GAD, and can, presumably, manufacture GABA. The reasons for their preferential use of the 67-kDa GAD isoform remain to be elucidated.

Acetylcholinesterase and choline acetyltransferase localization patterns do correspond in cat and rat retinas

Is acetylcholinesterase (AChE) a reliable marker for cholinergic activity in the cat and rat retinas? To evaluate this question, radial sections, labeled for AChE, have been compared to sections labeled for choline acetyltransferase (ChAT). Within the inner plexiform layer (IPL) of each species, two lightly-stained AChE bands are revealed which correspond to the depths of ChAT immunoreactivity. Although retinal AChE is not limited exclusively to sites where ChAT is present, AChE and ChAT activity do occur in the same IPL sublaminae. Used with proper caution, AChE is a reliable secondary indicator of cholinergic activity.

Cholinergic and GABAergic neurons occur in both the distal and proximal turtle retina

Turtle retinas were processed immunocytochemically and histochemically to detect the presence of choline acetyltransferase (ChAT), acetylcholinesterase (AChE), and glutamate decarboxylase (GAD). We observed cholinergic and gamma-aminobutyric acid (GABA)ergic neurons in the proximal retina, as expected, and in the distal retina as well. ChAT immunoreactivity in the distal retina was observed within the axons and pedicles of numerous cone photoreceptors, suggesting that a population of turtle cone photoreceptors uses ACh as a neurotransmitter. Type L2 horizontal cells were immunoreactive for GAD, and their dendrites invaginated into cone pedicles. AChE histochemistry revealed processes within the outer plexiform layer which formed a loosely organized lattice. In the proximal retina, labeling for ChAT and GAD was similar to that reported by previous investigators. Processes from ChAT-labeled amacrine cells in the inner nuclear layer formed a stratum within the distal inner plexiform layer (IPL) (at 16-21% relative IPL depth), and processes from ChAT-labeled amacrines in the ganglion cell layer formed a proximal ChAT stratum (at 55-58% relative IPL depth). In addition, six AChE-labeled bands and five GAD-labeled bands were observed within the IPL of stained retinas. Therefore, we determined that the two broadest AChE-labeled bands and the two broadest GAD-labeled bands overlapped the two labeled ChAT strata. The evidence for cholinergic and GABAergic processes in both the inner plexiform layer and the outer plexiform layer, combined with electrophysiological evidence from other investigators, raises the possibility that distal retinal neurons may be involved in the encoding of directional information.

Antiserum to lucifer yellow: preparation, characterization, and use for immunocytochemical localization of dye-filled retinal neurons

We present a new method for the preparation of antisera to Lucifer Yellow, and these antisera are here shown to be particularly suitable for immunocytochemical localization of multiple dye-injected cells in large pieces of vertebrate retina. The method involves the preparation of covalent conjugates of the VS isomer of Lucifer Yellow with keyhole limpet hemocyanin (KLH) or rabbit serum albumin (RSA), and their use as immunogens in rabbits. Both carrier protein conjugates yielded robust antibody responses. Antiserum to the KLH-LY conjugate contained precipitating antibodies against LY and KLH, although activity to the latter did not interfere with immunocytochemical staining. Rabbit antiserum to the RSA-LY conjugate contained precipitating antibody only against LY. When used for immunocytochemical staining of large retinal pieces containing many LY-filled cells, both antisera yielded well-stained, darkly filled cells similar to those seen with the Golgi technique; even very fine dendritic processes of retinal ganglion cells could be followed for long distances. LY immunocytochemistry provides a useful alternative to photooxidation for the analysis of multiple dye injected cells, especially in whole mounts. This approach may also be useful for immunocytochemical identification of cells filled with LY after tissue fixation.

Cholinergic amacrine neurons of the dogfish retina

In the mammalian retina, the dendritic arbors of cholinergic amacrine neurons have a unique starburst shape; these arbors lie in narrow sublaminae within the inner plexiform layer, where they provide input to a wide variety of ganglion cell types. Immunocytochemistry has been used to identify cholinergic cells in one poikilotherm, the goldfish (Tumosa et al., 1984), but there has been no description of the detailed dendritic morphology of these cells in the lower vertebrates. In the present study, cholinergic neurons have been characterized, by immunocytochemistry and dye filling, in the retina of the Pacific Coast dogfish, Squalus acanthias. The inner nuclear layer contained two populations of choline acetyltransferase-immunoreactive amacrine cells, of different sizes (average soma diameters 12.2 vs. 16.3 microns); 70% of the immunoreactive cells were of the smaller type. Cholinergic dendrites from these two cell populations formed two narrow strata within the inner plexiform layer, at depths of 14% and 31%. In the ganglion cell layer, 40% of the cells were immunoreactive for choline acetyltransferase (ChAT); these cells were very homogeneous in size, had an average diameter of 12.6 microns, and appeared to represent a single class of cholinergic amacrine. The dendrites of these cells formed a single, narrow stratum within the inner plexiform layer, at a depth of 59%. In living preparations, the smallest cell bodies in the ganglion cell layer were filled iontophoretically with Lucifer Yellow, under microscopic control. Such cells invariably had a stellate morphology; in many cases, they appeared quite similar to the starburst cholinergic amacrine cells described in rabbit and rat (Vaney, 1984; Voigt, 1986). Although double-label experiments failed to demonstrate ChAT immunoreactivity in specific dye-filled cells, the dendritic arbors of individual dye-filled stellate dogfish amacrines did co-stratify precisely with the proximal ChAT-immunoreactive sublamina of the inner plexiform layer. In addition, dye injection and ChAT immunocytochemistry appeared to label the same population of dogfish neurons, as suggested by the close structural similarity, and similar numerical proportion, of the cells identified with these two techniques. Similarities between the displaced cholinergic amacrine neurons of the dogfish retina, and the cholinergic, "starburst" amacrine neurons of the rabbit retina, are discussed.

Heterogeneity of GABAergic cells in cat visual cortex

Antibodies against neuropeptides and against a vitamin D-dependent calcium-binding protein (CaBP) label small cells with nonpyramidal-like morphology in the cat visual cortex (areas 17, 18, and 19). Since GABAergic cells are interneurons, a double-staining procedure was used to test for the coexistence of cholecystokinin (CCK), somatostatin (SRIF), neuropeptide Y (NPY), corticotropin-releasing factor (CRF), vasoactive intestinal polypeptide (VIP), and CaBP with glutamic acid decarboxylase (GAD). Our results show that CRF and VIP do not coexist with GAD, while the 3 other peptides and CaBP do. Hence GAD-positive cells can be subdivided into 4 broad groups: (1) cells that are only GAD-positive, (2) cells that are GAD- and CaBP-positive, (3) GAD-positive neurons also containing CCK, and (4) GAD-positive cells that also contain SRIF. A small subset of class 2 also contains SRIF and most cells of class 4 also contain NPY. The 4 classes of GAD-positive cells differ in laminar position: class 1 predominates in layers IV and V, classes 2 and 3 in the upper laminae (II and III), and class 4 in the deepest layer (VI).

Cholinergic neurons in the rabbit retina: dendritic branching and ultrastructural connectivity

The structure and synaptic connectivity of rabbit retinal cholinergic neurons have been studied with an immunocytochemical technique for the localization of choline acetyltransferase (ChAT). Cholinergic processes ramified in two narrow strata within the inner plexiform layer; viewed in the plane of the retina, each immunoreactive stratum took the form of a polygonal meshwork with openings of about 20 microns. There was frequently an extensive matching of the patterns of the two strata, such that openings in one meshwork lay directly over openings of similar size in the other meshwork. It is hypothesized that the pattern of branching of these cholinergic processes is a reflection of the branching pattern of ganglion cell dendrites in the cholinergic strata. The proximal cholinergic stratum was examined ultrastructurally, and had the following characteristics: (1) ChAT-immunoreactive processes made large numbers of synaptic contacts with ganglion cell dendrites; often there were many such ganglion cell dendrites running past each other at various angles within the plane of the cholinergic stratum; (2) cholinergic processes were never observed presynaptic to any other type of inner plexiform process; (3) the principal input onto cholinergic processes was provided by bipolar cell axon terminals; (4) ganglion cell dendrites within the cholinergic stratum also received direct bipolar input; and (5) unidentified (i.e. non-cholinergic and probably non-GABAergic) amacrine cell processes were often found that were presynaptic to these same ganglion cell dendrites, and that also formed reciprocal contacts with bipolar axon terminals within these synaptic complexes.

Cholinergic neurons in the rabbit retina: immunocytochemical localization, and relationship to GABAergic and cholinesterase-containing neurons

Cholinergic neurons have been identified in the rabbit retina by an immunocytochemical technique for the localization of choline acetyltransferase. The dendritic processes of these cells form two strata in the inner plexiform layer; these strata show almost no overlap with GABAergic strata (identified with glutamate decarboxylase immunocytochemistry) or with acetylcholinesterase (AChE) containing strata (identified with AChE cytochemistry), but the latter two overlap almost exactly. Implications of these data for the possible mechanisms of directional selectivity are discussed.

Localization of 3H-GABA, -muscimol, and -glycine in goldfish retinas stained for glutamate decarboxylase

Glutamic acid decarboxylase (GAD), the synthesizing enzyme for the neurotransmitter GABA, has been localized in goldfish retina using a new antiserum. We observed at least six types of GAD-immunoreactive amacrine cells, one of which was large and pyriform (Ab type). In addition, immunoreactive synaptic terminals were located throughout the inner plexiform layer (IPL). Amacrine cells that were GAD-immunoreactive also had high-affinity uptake mechanisms for both 3H-GABA and 3H-muscimol that were detectable autoradiographically. Type Ab pyriform amacrine cells were heavily labeled because of 3H-GABA uptake and were GAD-immunoreactive. Other types of GAD-immunoreactive amacrine cells, including a subpopulation of Ab amacrines, were lightly labeled because of 3H-GABA uptake. Because the same neurons that were GAD-immunoreactive also accumulated 3H-GABA and 3H-muscimol, these three are appropriate markers for GABAergic cells in the goldfish retina. However, the uptake of 3H-muscimol by many non-GAD-immunoreactive cells, detectable at longer autoradiographic exposure times, indicates that this label must be used with caution. Thirty percent of goldfish retinal amacrine cells are GABAergic, and their processes are distributed throughout all levels of the IPL. Few GAD-immunoreactive amacrine cells accumulated 3H-glycine, so the goldfish retina contains distinct populations of glycinergic and GABAergic amacrine cells.

Cytochrome oxidase staining reveals functional organization of monkey somatosensory thalamus

Histochemical staining for a mitochondrial enzyme, cytochrome oxidase demonstrates elongated, rod-like configurations of probable axon terminals in the trigeminal representation of the monkey somatic sensory thalamus. The stained rods are colocalized with similar aggregations of immunocytochemically stained GABAergic thalamic interneurons. Other data suggest the rods also contain clusters of relay neurons projecting to cortical columns, and they are here demonstrated as somatotopic units by micro-electrode mapping and the distribution of afferent fibers. Similar somatotopic rods can be revealed in the rest of the thalamic body representation by the reduction in cytochrome oxidase staining ensuing from the cutting of selected peripheral nerves.

Purification of L-glutamate decarboxylase from rabbit brain and preparation of a monospecific antiserum

L-Glutamate decarboxylase (GAD), the enzyme responsible for the biosynthesis of gamma-aminobutyric acid, has been purified from rabbit brain and used for the production of a monospecific rabbit antiserum. The enzyme was purified approximately 500-fold by a combination of ion exchange, hydrophobic, hydroxyapatite, and gel filtration column chromatography, and preparative polyacrylamide gel electrophoresis. The preparation thus obtained was injected into a rabbit, producing a polyspecific antiserum. This first antiserum was used for the preparation of an immunoprecipitate containing GAD; injections of the immunoprecipitate into a second rabbit led to the production of a second, monospecific anti-GAD serum. The specificity of the antiserum for GAD has been demonstrated by enzyme precipitation, immunodiffusion, line immunoelectrophoresis, gel filtration chromatography of GAD/anti-GAD immune complexes, and immunocytochemistry in the rat cerebellum.

Retinal GABA neurons: localization in vertebrate species using an antiserum to rabbit brain glutamate decarboxylase

Retinal gamma-aminobutyric acid (GABA) neurons have been localized immunocytochemically using a new antiserum against rabbit brain glutamate decarboxylase (GAD). The animals examined were: dogfish, ratfish, goldfish, catfish, turtle, chick, mouse, rat, pig, rabbit, cat and New World monkey. GAD-containing processes, observed as punctate deposits of immunochemical reaction product, formed discrete bands within the inner plexiform layers of all retinas examined. Immunoreactive, and therefore presumably GABAergic, amacrine cells were observed in all species. Displaced GABAergic amacrine cells were observed in the retinas of goldfish, catfish, turtle and chick, and sparsely in the rabbit as well. GABAergic horizontal cells were detected in catfish, goldfish, chick and turtle. Interplexiform cells in the cat and the rat were clearly immunoreactive for glutamate decarboxylase; this is the first report of GABAergic interplexiform cells in the rat.

Variation in susceptibility to atherosclerosis among inbred strains of mice

Ten inbred strains of mice were fed an atherogenic diet containing 1.25% cholesterol, 0.5% cholic acid and 15% fat. The strains were examined for plasma cholesterol and triglyceride levels and for formation of lipid-containing lesions in the aortic wall. The strains differed considerably in the frequency of lesion formation after 14 weeks on the atherogenic diet with a range of 0-1.8 lesions/mouse. The order of susceptibility to lesion formation from the least susceptible to the most susceptible was BALB/cJ, C3H/J, A/J, SWR/J, NZB/J, less than 129/J, AKR/J, DBA/2J, less than C57L/J less than C57BL/6J. Total plasma cholesterol after 5 weeks on the diet varied from 131 mg/dl to 328 mg/dl among strains; however, there was little correlation between total cholesterol levels and susceptibility to lesion formation (r = 0.29). Plasma triglycerides after 5 weeks on the diet varied less than cholesterol with a range of 137-220 mg/dl. An analysis of the genetic differences among inbred strains of mice might provide useful insights into lipid metabolism and the development of atherosclerosis.

Improved immunocytochemical staining through the use of Fab fragments of primary antibody, Fab-specific second antibody, and Fab-horseradish peroxidase

A modification of the unlabeled antibody method of immunocytochemistry is described here that offers increased immunoreagent penetration and greatly reduced background staining. The method involves the following alterations to the conventional technique; the use of Fab fragments of primary antibody, rather than whole immunoglobulin G (IgG) or serum; the use of a second, or link, anti-rabbit IgG serum that is Fab fragment-specific, rather than directed against the whole rabbit IgG molecule; the use of the Fab--horseradish peroxidase complex described by JR Slemmon, PM Salvaterra, and K Saito (J Histochem Cytochem 28:10, 1980), rather than peroxidase--antiperoxidase (PAP). Steps 2 and 3 alone brought about a significant reduction in background staining, but did not increase the depth of immunostaining, as compared to the PAP technique. When all three steps were combined, however, background staining was further reduced, and there was a five- to tenfold increase in the depth of immunostaining. These readily made changes should be useful in preembedding immunocytochemistry whenever enhanced reagent penetration is required.

Neuropeptide-containing neurons of the cerebral cortex are also GABAergic

Neurons in the cat and monkey cerebral cortex were stained immunocytochemically for glutamic acid decarboxylase (GluDCase; L-glutamate 1-carboxy-lyase, EC 4.1.1.15), somatostatin (SRIF), neuropeptide Y (NPY), and cholecystokinin octapeptide (CCK). In all areas of cortex examined (somatic sensory, motor, parietal and visual areas), neurons displaying immunoreactivity for each of these molecules were nonpyramidal cells. Co-localization of GluDCase immunoreactivity with peptide immunoreactivity in the same cells was demonstrated by (i) the antibody elution method, staining the same cells by immunofluorescence, first for a peptide and then for GluDCase; (ii) double staining of the same sections with sheep anti-GluDCase and rabbit anti-peptide antisera, the bound antibodies being localized by rhodamine-conjugated donkey anti-sheep and fluorescein-conjugated swine anti-rabbit secondary antisera. With both procedures, cell bodies immunoreactive for GluDCase and for each of the peptides were found in all areas of cortex examined. With double labeling on single sections, it was found that all CCK-, SRIF-, and NPY-immunoreactive cells in cat cortex and 90%-95% in monkey cortex are also GluDCase positive. Many more cells, however, are immunoreactive for GluDCase alone. GluDCase was co-localized with CCK, SRIF, or NPY not only in cell somata, but also in small punctate structures, which are likely to be axon terminals. From the data gained in previous electron microscopic studies, we postulate that neurons displaying GluDCase- and CCK-like immunoreactivity are a class separate from those displaying GluDCase- and SRIF-like immunoreactivity. NPY, however, is co-localized with SRIF immunoreactivity. These results imply that classes of cortical interneuron contain a conventional neurotransmitter (gamma-aminobutyric acid) and a neuromodulator (one of the peptides).

L-glutamic acid: a neurotransmitter candidate for cone photoreceptors in human and rat retinas

We have combined immunocytochemical localization of L-aspartate aminotransferase (L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1; glutamic-oxaloacetic transaminase) with autoradiographic localization of high-affinity uptake sites for L-glutamate or L-aspartate to identify the neurotransmitters of mammalian photoreceptors. In both human and rat retinas, high aspartate aminotransferase immunoreactivity is found in cones but not in rods; certain putative bipolar and amacrine cells are also heavily stained. In the human retina, and perhaps also in the rat retina, cones possess a high-affinity uptake mechanism for L-glutamate but not L-aspartate, whereas rods and Müller (glial) cells take up both L-glutamate and L-aspartate. Taken together, our results indicate that (i) L-glutamate is much more likely than L-aspartate to be the transmitter for human cones, and possibly for cones of other mammalian species as well, and (ii) major differences exist between mammalian cones and rods in the transport and metabolism or utilization of L-aspartate and L-glutamate.

The ultrastructure of rat rod synaptic terminals: effects of dark-adaptation

The ultrastructure of synaptic terminals of rat rod photoreceptors was studied in light-adapted and dark-adapted states. In the light-adapted state, horizontal cell processes embedded in the photoreceptor terminal show smooth surface contours and are ovoid in cross section. In the dark-adapted state, fingerlike protrusions of photoreceptor cytoplasm extend into the horizontal cell processes on either side of the synaptic ribbon. An electron-dense structure lies under the horizontal cell membrane that surrounds these fingerlike protrusions. This submembrane specialization is generally associated with areas of concavity of the horizontal cell membrane; it occurs in goldfish rods as well as rat rods. The protrusions and the horizontal cell specialization may be involved in membrane dynamics during synaptic activity.

The gamma-aminobutyric acid system in rabbit retina: localization by immunocytochemistry and autoradiography

The localization of gamma-aminobutyric acid (GABA) neurons in the rabbit retina has been studied by immunocytochemical localization of the GABA-synthesizing enzyme L-glutamate decarboxylase (L-glutamate I-carboxy-lyase, EC 4.1.1.15) and by [3H]GABA uptake autoradiography. When Triton X-100 was included in immunocytochemical incubations with a modified protein A-peroxidase-antiperoxidase method, reaction product was found in four broad, evenly spaced laminae within the inner plexiform layer. In the absence of the detergent, these laminae were seen to be composed of small, punctate deposits. When colchicine was injected intravitreally before glutamate decarboxylase staining, cell bodies with the characteristic shape and location of amacrine cells were found to be immunochemically labeled. Intravitreally administered [3H]GABA produced a diffuse labeling of the inner plexiform layer and a dense labeling of certain amacrine cell bodies in the inner nuclear layer. Both immunocytochemical and autoradiographic results support the notion that certain, if not all, amacrine cells use GABA as their neurotransmitter.