Ultrasound-guided subcostal transversus abdominis plane blocks with liposomal bupivacaine vs. non-liposomal bupivacaine for postoperative pain control after laparoscopic hand-assisted donor nephrectomy: a prospective randomised observer-blinded study.

We compared the effect of subcostal transversus abdominis plane (TAP) block with liposomal bupivacaine to TAP block with non-liposomal bupivacaine on postoperative maximal pain scores in patients undergoing donor nephrectomy. Sixty patients were prospectively randomly assigned to receive ultrasound-guided bilateral TAPs with either 1.3% liposomal bupivacaine and normal saline or 0.25% non-liposomal bupivacaine with adrenaline. There was a significant decrease in maximal pain scores in the liposomal bupivacaine TAP group when compared with the non-liposomal bupivacaine group median (IQR [range]), 24-48 h after injection, 5 (3.0-5.2 [0-10]) vs. 6 (4.5-7.0 [1--9]) p = 0.009; 48-72 h after injection, 3 (2.0-5.0 [0-8]) vs. 5 (3.0-7.0 [0-10]) p = 0.02; and in opioid use 48-72 h after injection, mean (SD) µg equivalents of fentanyl 105 (97) vs. 182 (162) p = 0.03. Liposomal bupivacaine via subcostal TAP infiltration provided superior analgesia up to 72 h after injection when compared with non-liposomal bupivacaine.

MRI evaluation of foraminal changes in the cervical spine with assistance of a novel compression device.

Standard supine Magnetic Resonance Imaging (MRI) does not acquire images in a position where most patients with intermittent arm radiculopathy have symptoms. The aim of this study was to test the feasibility of a new compression device and to evaluate image quality and foraminal properties during a Spurling test under MRI acquisition. Ten asymptomatic individuals were included in the study (6 men and 4 women; age range 27 to 55 years). First, the subjects were positioned in the cervical compression device in a 3 T MRI scanner, and a volume T2 weighted (T2w) sequence was acquired in a relaxed supine position (3 min). Thereafter, the position and compressive forces on the patient's neck (provocation position) were changed by maneuvering the device from the control room, with the aim to simulate a Spurling test, causing a mild foraminal compression, followed by a repeated image acquisition (3 min). A radiologist measured the blinded investigations evaluating cervical lordosis (C3-C7), foraminal area on oblique sagittal images and foraminal cross-distance in the axial plane. A total of three levels (C4-C7) were measured on the right side on each individual. Measurements were compared between the compressed and relaxed state. Reliability tests for inter- and intraclass correlation were performed. The device was feasible to use and well tolerated by all investigated individuals. Images of adequate quality was obtained in all patients. A significant increase (mean 9.4, p = 0.013) in the cervical lordosis and a decreased foraminal cross-distance (mean 32%, p < 0.001) was found, during the simulated Spurling test. The area change on oblique sagittal images did not reach a statistically significant change. The reliability tests on the quantitative measures demonstrated excellent intraobserver reliability and moderate to good interobserver reliability. Applying an individualized provocation test on the cervical spine, which simulates a Spurling test, during MRI acquisition was feasible with the novel device and provided images of satisfactory quality. MRI images acquired with and without compression showed changes in cervical lordosis and foraminal cross distance indicating the possibility of detecting changes of the foraminal properties. As a next step, the method is to be tested on symptomatic patients.

A selective human beta3 adrenergic receptor agonist increases metabolic rate in rhesus monkeys.

Activation of beta3 adrenergic receptors on the surface of adipocytes leads to increases in intracellular cAMP and stimulation of lipolysis. In brown adipose tissue, this serves to up-regulate and activate the mitochondrial uncoupling protein 1, which mediates a proton conductance pathway that uncouples oxidative phosphorylation, leading to a net increase in energy expenditure. While chronic treatment with beta3 agonists in nonprimate species leads to uncoupling protein 1 up-regulation and weight loss, the relevance of this mechanism to energy metabolism in primates, which have much lower levels of brown adipose tissue, has been questioned. With the discovery of L-755,507, a potent and selective partial agonist for both human and rhesus beta3 receptors, we now demonstrate that acute exposure of rhesus monkeys to a beta3 agonist elicits lipolysis and metabolic rate elevation, and that chronic exposure increases uncoupling protein 1 expression in rhesus brown adipose tissue. These data suggest a role for beta3 agonists in the treatment of human obesity.

Continuous Paravertebral Infusions as an Effective Adjunct for Postoperative Pain Management in Living Liver Donors: A Retrospective Observational Study.

We analyzed the effectiveness of paravertebral-block for immediate postoperative pain control in living liver donors. Specifically, we sought to determine whether or not the addition of paravertebral catheters with continuous ropivacaine infusion would decrease postoperative opioid use and reduce the incidence of adverse effects and complications. We reviewed the records of 26 patients who underwent right-lobe living donor hepatectomy (RLDH): 16 with and 10 without such catheters. The primary outcome was opioid use on postoperative day (POD) 1 through 3. For each of those 3 days, we calculated each patient's opioid use in morphine equivalents (mg). We also noted pain scores, adverse effects, and complications. The rate of decrease in morphine equivalents was higher in the catheter group (rate of change = -22.72; P = .038) for POD 1 (0-24 hours) and POD 2 (25-48 hours) than in the noncatheter group. For POD 2 alone, the catheter group used, on average, 20.98 mg fewer morphine equivalents than the noncatheter group (P = .023). The catheter group had a markedly reduced pain trajectory postoperatively (P = .014) than the noncatheter group. The catheter placement procedure itself was safe.

Novel gene sequences expressed by human melanoma cells identified by molecular subtraction.

Despite the variety of approaches used, only a limited number of tumor-associated antigens have been described for each histological type of tumor. In this report, we present a new strategy involving molecular subtraction to identify novel melanoma-associated gene sequences. Toward this end, 156 complementary DNA clones were isolated with a subtracted melanoma complementary DNA probe (melanoma minus lung carcinoma) after screening 2 x 10(4) independent recombinants of a melanoma expression library by in situ plaque hybridization. These clones were then polymerase chain reaction amplified, screened for duplication, and categorized into 53 discrete genes. By applying poissonian distribution to the numbers of duplicate isolates, we found most of the genes to be rare messages, present at less than 1 copy/200 molecules of mRNA in a typical somatic cell. Messages specific for a type of tissue are usually expressed in this range. The expression of the 53 genes was further studied in human tumor cell lines and normal tissues. Partial sequence data obtained for 20 complementary DNA clones revealed 8 novel human genes. The mRNA transcripts for 5 of the novel genes were identified by Northern blot analysis. Thus, molecular subtraction appears to be applicable for the identification of novel tumor-associated sequences. Some of the potential advantages and limitations of this technology are discussed, including its application to the molecular characterization of immunogenic melanoma-associated antigens.

Distribution of mono-, di, and tri-O-acetylated sialic acids in normal and neoplastic colon.

The purpose of this study was to compare the expression of O-acetylated sialic acids on normal colonic epithelial cells to that on primary and metastatic human adenocarcinoma of the colon and rectum. In 24 cases, the relative percentages of biosynthetically labeled non-, mono-, di-, and tri-O-acetylated sialic acids were measured after hydrolytic release, separation, and identification by paper chromatography. In one case, the presence of di- and tri-O-acetylated sialic acids was confirmed by fast atom bombardment-mass spectral analysis. Differences were observed in the expression of sialic acids between normal colonic epithelium, "uninvolved" colon mucosa remote to a colonic adenocarcinoma, and colonic adenocarcinoma. The levels of mono- and tri-O-acetylated sialic acids accounted for the difference in the ratios of sialic acids expressed between normal and "uninvolved" colonic mucosa, while the total amount of O-acetylation was unchanged. However, no difference was observed in the relative amounts of non- and O-acetylated sialic acids between either fresh and tissue culture-established colon carcinomas, or fresh and tissue culture-established liver metastasis derived from carcinoma of the colon. The relative expression of these O-acetylated sialic acids molecules appears to vary according to tissue type. This study suggests that individuals with adenocarcinoma of the colon express a field defect resulting in abnormal ratios of O-acetylated sialic acids.

Phosphatidylserine is a global immunosuppressive signal in efferocytosis, infectious disease, and cancer.

Apoptosis is an evolutionarily conserved and tightly regulated cell death modality. It serves important roles in physiology by sculpting complex tissues during embryogenesis and by removing effete cells that have reached advanced age or whose genomes have been irreparably damaged. Apoptosis culminates in the rapid and decisive removal of cell corpses by efferocytosis, a term used to distinguish the engulfment of apoptotic cells from other phagocytic processes. Over the past decades, the molecular and cell biological events associated with efferocytosis have been rigorously studied, and many eat-me signals and receptors have been identified. The externalization of phosphatidylserine (PS) is arguably the most emblematic eat-me signal that is in turn bound by a large number of serum proteins and opsonins that facilitate efferocytosis. Under physiological conditions, externalized PS functions as a dominant and evolutionarily conserved immunosuppressive signal that promotes tolerance and prevents local and systemic immune activation. Pathologically, the innate immunosuppressive effect of externalized PS has been hijacked by numerous viruses, microorganisms, and parasites to facilitate infection, and in many cases, establish infection latency. PS is also profoundly dysregulated in the tumor microenvironment and antagonizes the development of tumor immunity. In this review, we discuss the biology of PS with respect to its role as a global immunosuppressive signal and how PS is exploited to drive diverse pathological processes such as infection and cancer. Finally, we outline the rationale that agents targeting PS could have significant value in cancer and infectious disease therapeutics.

The chicken junD gene and its product.

We have isolated and characterized the chicken junD gene. It does not contain an intron; its upstream regulatory sequences lack the AP-1-binding site seen in c-jun but include two CRE elements. Downstream untranslated sequences do not show the destabilizing signal ATTTA. The amino acid sequence of the chicken JunD protein is closely related to that of mouse JunD in the dimerization and DNA contact surfaces of the carboxy-terminal region; additional homologies to mouse JunD are seen in acidic and amphipathic amino-terminal domains. Chicken JunD contains stretches of oligoglycines, alanines and prolines, possibly acting as hinges that connect functionally distinct domains of the protein. Chicken junD is broadly expressed at low basal levels in differentiated tissues and at somewhat higher levels in cultured fibroblasts. The cDNA clone of junD was transcribed and translated in vitro. The resulting JunD protein migrates in between 40 and 50 kDa in an SDS gel and can be precipitated with an antibody prepared against a polypeptide consisting of the carboxy-terminal 100 amino acids of mouse c-Jun.

The C-terminal regulatory domain of p53 contains a functional docking site for cyclin A.

Radiation injury to cells enhances C-terminal phosphorylation of p53 at both Ser315 and Ser392 in vivo, suggesting the existence of two cooperating DNA damage-responsive pathways that play a role in stimulating p53-dependent gene expression. Our previous data has shown that cyclin A-cdk2 is the major enzyme responsible for modifying p53 at Ser315 in vivo after irradiation damage and in this report we dissect the mechanism of cyclinA-cdk2 binding to and phosphorylation of p53. Although cyclin B(1)-dependent protein kinases can phosphorylate small peptides containing the Ser315 site, cyclin A-cdk2 does not phosphorylate such small peptides suggesting that additional determinants are required for cyclin A-cdk2 interaction with p53. Peptide competition studies have localized a cyclin A interaction site to a Lys381Lys382Leu383Met384Phe385 sequence within C-terminal negative regulatory domain of human p53. An alanine mutation at any one of four key positions abrogates the efficacy of a synthetic peptide containing this motif as an inhibitor of cyclin A-cdk2 phosphorylation of p53 protein. Single amino acid mutations of full-length p53 protein at Lys382, Leu383, or Phe385 decreases cyclin A-cdk2 dependent phosphorylation at Ser315. Cyclin B(1)-cdk2 complexes are not inhibited by KKLMF motif-containing peptides nor is p53 phosphorylation by cyclin B-cdk2 reduced by mutation of the cyclin A interaction site. These data identifying a KKLMF cyclin A docking site on p53 protein highlight a common cyclin A interaction motif that is shared between the tumour suppressor proteins pRb and p53.

Evaluation of the VIDAS Listeria (LIS) immunoassay for the detection of Listeria in foods using demi-Fraser and Fraser enrichment broths, as modification of AOAC Official Method 999.06 (AOAC Official Method 2004.06).

A multilaboratory study was conducted to compare the VIDAS LIS immunoassay with the standard cultural methods for the detection of Listeria in foods using an enrichment modification of AOAC Official Method 999.06. The modified enrichment protocol was implemented to harmonize the VIDAS LIS assay with the VIDAS LMO2 assay. Five food types--brie cheese, vanilla ice cream, frozen green beans, frozen raw tilapia fish, and cooked roast beef--at 3 inoculation levels, were analyzed by each method. A total of 15 laboratories representing government and industry participated. In this study, 1206 test portions were tested, of which 1170 were used in the statistical analysis. There were 433 positive by the VIDAS LIS assay and 396 positive by the standard culture methods. A Chi-square analysis of each of the 5 food types, at the 3 inoculation levels tested, was performed. The resulting average Chi square analysis, 0.42, indicated that, overall, there are no statistical differences between the VIDAS LIS assay and the standard methods at the 5% level of significance.

Substrate specificity determinants of the checkpoint protein kinase Chk1.

The Chk1 protein kinase plays a critical role in a DNA damage checkpoint pathway conserved between fission yeast and animals. We have developed a quantitative assay for Chk1 activity, using a peptide derived from a region of Xenopus Cdc25C containing Ser-287, a known target of Chk1. Variants of this peptide were used to determine the residues involved in substrate recognition by Chk1, revealing the phosphorylation motif Phi-X-beta-X-X-(S/T)*, where * indicates the phosphorylated residue, Phi is a hydrophobic residue (M>I>L>V), beta is a basic residue (R>K) and X is any amino acid. This motif suggests that Chk1 is a member of a group of stress-response protein kinases which phosphorylate target proteins with related specificities.

Platelet-derived growth factor receptors of mouse central nervous system cells in vitro.

This study evaluates the distribution of receptors for platelet-derived growth factor (PDGF) on central nervous cells maintained in vitro using colloidal gold-labeled immunocytochemical markers at the electron microscopic level. Platelet-derived growth factor receptors were found to be sparsely distributed over the surface of type 1 astrocytes, apparent type 2 astrocytes, and neurons. Receptors appeared to be preferentially associated with filopodia-like extensions of the cell membrane. The existence of functional receptors was confirmed using the impermeant, water-soluble affinity cross-linking agent bis(sulfosuccinimidyl)suberate to covalently link radiolabeled PDGF to its receptor. The PDGF/receptor complexes could also be immunoprecipitated with the same antibody used in immunocytochemical experiments. The improved resolution of these techniques allows definitive identification of PDGF receptors on cultured mammalian central nervous system cells other than oligodendrocytes. These data expand the range of possible roles of PDGF during nervous system development. Receptors for PDGF are likely to play a key role in the differentiation of cells in the central nervous system.

Development of acetylcholinesterase activity in the lateral geniculate nucleus.

The pattern of acetylcholinesterase activity in the tree shrew (Tupaia belangeri) lateral geniculate nucleus (LGN) undergoes a number of striking changes during postnatal development. The adult tree shrew LGN is made up of six cellular layers divided by relatively cell-free interlaminar zones. At birth, however, the nucleus appears unlaminated when processed with conventional Nissl-staining techniques. The cellular lamination appears during the first postnatal week. The eyes open much later, typically at the end of the third week after birth. In the adult tree shrew, acetylcholinesterase (AChE) activity is found throughout the nucleus (both within and between the six cellular layers). In most sections examined, reaction product is slightly more intense in the lateral cell layers (4, 5, and 6). This is in sharp contrast to the pattern at birth (postnatal day zero, or P0). The detectable AChE activity at this age is apparently found in inchoate layers 1-2 and 4-5. Within these pairs, areas innervated by the ipsilateral eye (i.e., incipient layers 1 and 5) appear to contain more reaction product. From P0 to P4, the density of AChE activity increases in layers 1-2 and 4-5 and becomes detectable in the barely evident layers 3 and (usually) 6 at this age. By the middle of the second postnatal week, after laminae are clearly apparent with a Nissl stain, AChE activity has increased and is mainly associated with each cellular layer in the nucleus. During the third week after birth this pattern undergoes a radical shift. The most intense AChE activity is now in the interlaminar zones. Finally, as the adult pattern emerges, AChE activity increases in the cellular layers and all areas of the nucleus exhibit relatively high levels of AChE activity. Superimposed on this changing laminar pattern of AChE activity are changes related to the retinotopic map within the nucleus. Portions of the LGN representing central vision develop their characteristic pattern of activity several days ahead of the regions representing more peripheral visual field locations. AChE activity is also found transiently in the optic tract near the LGN during the first 3 postnatal weeks. Two (possibly three) groups of AChE-carrying fibers can be traced from the optic chiasm to their apparent sites of termination (or origin) in the parabigeminal nucleus, ventral lateral geniculate nucleus, and dorsal LGN. The activity present in the optic tract disappears shortly after eye opening.(ABSTRACT TRUNCATED AT 400 WORDS)

Development of the lateral geniculate nucleus: interactions between retinal afferent, cytoarchitectonic, and glial cell process lamination in ferrets and tree shrews.

We have studied the relationship of retinal afferents, glial cell processes, and neuronal cytoarchitectonics in the lateral geniculate nucleus (LGN) of two species: tree shrews (Tupaia belangeri) and ferrets (Mustela putoris). Both species are relatively immature at birth, allowing the development of these features to be studied in the perinatal period. Retinal afferents, visualized by intraocular injection of a wheat germ agglutinin/horseradish peroxidase conjugate (WGA-HRP), are apparently the first elements of the developing LGN to exhibit a characteristic layered pattern in tree shrews and ferrets. Some radial glia still remain in the LGN of both species as the retinal afferents are in the process of segregating. Glial cell processes were visualized immunohistochemically with antibodies to glial fibrillary acidic protein (GFAP) or vimentin. In both the ferret and tree shrew, layering of glial cell processes is first seen as the overlap of retinal terminal fields diminishes. In the tree shrew LGN, these bands of dense glial cell staining are seen in apparent future cellular layers, whereas in the ferret, glial cell banding appears in interlaminar zones. If one or both eyes are removed at birth in tree shrews (before LGN cell layers are formed), the glial cell pattern seen 1 week later is in accord with the distribution of surviving nerve cells. The glial processes do not appear to invade regions left by degenerating retinal terminals or dying LGN cells. Several days after the appearance of layered glial cell processes (in the tree shrew) or at about the same time as glial layering (in the ferret), the first interlaminar spaces develop between neuronal cells, marking the beginning of cytoarchitectonic lamination, with its distinctive alternating cell-rich and cell-poor zones. Over the next several weeks, LGN neurons in both species continue to segregate into characteristic layers until the final, adult pattern of neuronal lamination is evident; as this process is completed, glial cell lamination disappears. These observations suggest that glial cells may be involved in establishing the neuronal layers that characterize the mature LGN of many species.

Production of monoclonal antibodies using recombinant baculovirus displaying gp64-fusion proteins.

Generation of protein immunogens is often a rate-limiting step in the production of monoclonal antibodies (Mabs). Expressing domains of proteins as fusions to the baculovirus surface glycoprotein gp64 displays foreign proteins on the surface of the virion. Antigen is produced by inserting a gene fragment in-frame between the signal sequence and the mature protein domain of the gp64 nucleotide sequence. This method allows immunization with whole virus, eliminating the need for purification of target antigens. Affinity-matured Mabs to the human nuclear receptors LXRbeta and FXR have been produced using baculovirus particles displaying gp64/nuclear receptor fusion proteins as the immunizing agent. Immunizations were performed directly with pelleted virus using the Repetitive Immunization Multiple Sites (RIMMS) immunization strategy for rapid Mab production. All Mabs were identified using insect cells infected with the immunizing virus. Characterization of these antibodies shows them to be class-switched and specific for LXRbeta or FXR. Additionally, high affinity antibodies that recognize gp64 and neutralize baculovirus infection of insect cells were isolated. Use of the recombinant baculovirus gp64 display system makes possible the production of Mabs once a partial DNA sequence is known. This allows the generation of antibodies prior to the isolation of purified protein, in turn providing antibodies to facilitate purification, characterization and immunolocalization of proteins.

Acetylcholine receptors in the human retina.

Evidence for a population of acetylcholine (ACh) receptors in the human retina is presented. The authors have used the irreversible ligand 3H-propylbenzilylcholine mustard (3H-PrBCM) to label muscarinic receptors. 3H- or 125I-alpha-bungarotoxin (alpha-BTx) was used to label putative nicotinic receptors. Muscarinic receptors are apparently present in the inner plexiform layer of the retina. Autoradiographic grain densities are reduced in the presence of saturating concentrations of atropine, quinuclidinyl benzilate or scopolamine; this indicates that 3H-PrBCM binding is specific for a population of muscarinic receptors in the human retina. Binding sites for radiolabeled alpha-BTx are found predominantly in the inner plexiform layer of the retina. Grain densities are reduced in the presence of d-tubocurarine, indicating that alpha-BTx may bind to a pharmacologically relevant nicotinic ACh receptor. The work reported here is consistent with earlier data on cholinergic neurons in the retina of other mammalian species, as well as with previous work on the psychophysical effects of cholinergic agonists on human vision. This study provides evidence for cholinergic neurotransmission in the human retina.

Purification of adenovirus hexon by high performance liquid chromatography.

Hexon is the major structural protein of adenovirus, and has significance in studies of virus structure and function, vaccine development, and immunodiagnosis. We describe a simple, single-step, anion-exchange high performance liquid chromatography (HPLC) method for the high yield purification of hexon. Purity of the isolated hexon was assessed by SDS-PAGE and HPLC methods. The isolated hexon was immunologically reactive with anti-hexon monoclonal antibody in a dot-blot assay. It also retained immunogenicity, as polyclonal antisera from rabbits immunized with hexon showed the desired antigen specificity. The enhanced speed of this purification method allows for the efficient isolation of hexon from various serotypes, and thus may facilitate comparative studies of hexon immunobiology.

Acetylcholinesterase in the human retina.

The distribution of cholinesterase activity in the human retina was evaluated using histochemical methods. The butyrylcholine esterase (BuChE) inhibitor tetraisopropylpyrophosphoramide was used to localize acetylcholinesterase (AChE) activity, the AChE inhibitor BW284c51 was used to localize BuChE activity, and eserine was used to inhibit all cholinesterase activity in control incubations. We have found specific AChE activity in the inner plexiform layer (IPL) and BuChE activity is apparently associated with blood vessels at the light microscopic level. At the electron microscopic level, AChE reaction product is seen both at apparently synaptic and manifestly non-synaptic sites. Reaction product is found adjacent to neural processes in the IPL; these processes have an ultrastructure characteristic of amacrine cells. Although reaction product is seen adjacent to bipolar, ganglion and Müller cells, it is only present where they come into contact with apparent amacrine cell profiles. Using longer incubations, reaction product is found in the perikarya of cells with the morphology and position of amacrine and displaced amacrine cells. There is also some evidence for AChE activity adjacent to lateral processes at a rare type of rod synapse in the outer plexiform layer. The observations reported here strengthen the evidence for cholinergic neurotransmission in the human retina.

Muscarinic cholinergic receptors in the retina of the larval tiger salamander.

The pharmacology and autoradiographic localization of muscarinic cholinergic receptors in retinal slices of the larval tiger salamander have been examined using the muscarinic antagonist [3H]propylbenzilylcholine mustard. Under the conditions of these experiments the binding of this ligand is irreversible. Saturation and maximum specific binding of 270 pM of ligand per gram protein are observed after an incubation of 1 h, and autoradiographic studies show that this does not reflect surface binding alone. Muscarinic but not nicotinic drugs suppress the binding of propylbenzilylcholine mustard at physiologically relevant concentrations; half-maximal suppression of binding by the muscarinic antagonists atropine sulfate and quinuclidinyl benzilate occurs, respectively, at 9.0 and 7.5 X 10(-10) M. Light microscopic autoradiography reveals the discrete localization of the ligand to the sites of synaptic contact, the retinal plexiform layers, predominantly the inner plexiform layer. The implications of the present study on current theories of cholinergic function in the vertebrate retina are discussed.

Localization of cholinesterase activity in the outer plexiform layer of the larval tiger salamander retina.

Acetylcholinesterase activity, which may be indicative of cholinergic synapses, has been ultrastructurally localized in the outer plexiform layer of the larval tiger salamander retina using the cholinesterase staining method of Karnovsky and Roots. In the presence of the butyrylcholinesterase inhibitor, ethopropazine, precipitate is localized to discrete 'stain laminae' about 300 nm in their largest dimension and bounded by a 10 nm wide electron-lucent gap. Stain laminae are predominantly found adjacent to horizontal cell axon terminals which were identified by serial section analysis. Stain precipitate has not been found associated with horizontal cell dendrites and in only one case was a lamina found adjacent to a bipolar cell dendrite. Intracellular deposits of cholinesterase stain precipitate were also observed. In some cases, stain is found adjacent to synaptic ribbons in photoreceptor terminals. Likely artifacts appear to have been ruled out by control experiments in which retinas either were not treated with cholinesterase stain or were treated in the presence of the specific acetylcholinesterase inhibitor, BW284C51. Thus, the stain laminae probably result from specific, highly localized areas of acetylcholinesterase activity. The implications of the present study on current theories of cholinergic function in the vertebrate retina are discussed.