Involvement of the MAP kinase ERK2 in MUC1 mucin signaling

MUC1 mucin is a receptor-like glycoprotein expressed abundantly in various cancer cell lines as well as in glandular secretory epithelial cells, including airway surface epithelial cells. The role of this cell surface mucin in the airway is not known. In an attempt to understand the signaling mechanism of MUC1 mucin, we established a stable cell line from COS-7 cells expressing a chimeric receptor consisting of the extracellular and transmembrane domains of CD8 and the cytoplasmic (CT) domain of MUC1 mucin (CD8/MUC1 cells). We previously observed that treatment of these cells with anti-CD8 antibody resulted in tyrosine phosphorylation of the CT domain of the chimera. Here we report that treatment of CD8/MUC1 cells with anti-CD8 resulted in activation of extracellular signal-regulated kinase (ERK) 2 as assessed by immunoblotting, kinase assay, and immunocytochemistry. The activation of ERK2 was completely blocked either by a dominant negative Ras mutant or in the presence of a mitogen-activated protein kinase kinase (MEK) inhibitor. We conclude that tyrosine phosphorylation of the CT domain of MUC1 mucin leads to activation of a mitogen-activated protein kinase pathway through the Ras-MEK-ERK2 pathway. Combined with the existing data by others, it is suggested that one of the roles of MUC1 mucin may be regulation of cell growth and differentiation via a common signaling pathway, namely the Grb2-Sos-Ras-MEK-ERK2 pathway.

Nesidioblastosis and mixed hamartoma of the liver in Beckwith-Wiedemann syndrome: case study including analysis of H19 methylation and insulin-like growth factor 2 genotyping and imprinting

An infant with persistent hyperinsulinemic hypoglycemia, diffuse nesidioblastosis, and mixed hamartoma of the liver (MHL), in addition to demonstrating clinical, pathologic, and molecular manifestations of Beckwith-Wiedemann syndrome (BWS), is the subject of this report. H19 methylation assay and allelic expression analysis for insulin-like growth factor 2 (IGF2) indicated that the patient was mosaic for paternal isodisomic cells and normal cells in lung tissue, nontumoral liver tissue, tissue from the MHL, and pancreatic tissue. We propose that abundant IGF2 expression during development due to paternal isodisomy resulted in hepatomegaly and islet cell hyperplasia, which led to nesidioblastosis. MHL, by contrast, may have resulted from a decrease in disomic cells, compared with nontumoral liver tissue, which showed an increase in disomic cells. Thus, somatic mosaicism may result in unbalanced tissue growth, which may contribute to the formation of MHL in BWS.

In vivo antitumor effect of herpes simplex virus thymidine kinase gene therapy in rat hepatocellular carcinoma: feasibility of adenovirus-mediated intra-arterial gene delivery

Transfer of the herpes simplex virus-thymidine kinase gene, followed by the administration of ganciclovir (HSV-tk/GCV), has been a major approach for cancer gene therapy. We investigated the antitumor effect of the HSV-tk/GCV strategy with the rat orthotopic hepatocellular carcinoma (HCC) model and the tumor-selective gene delivery by an adenovirus-mediated gene transfer through the hepatic artery. The complete antitumor effect was demonstrated, after the treatment with GCV in rat HCC established by the implantation of HSV-tk transferred rat HCC cells. The in vivo bystander effect was also observed. The marked infiltration of CD4+ and CD8+ T lymphocytes, macrophages and NK cells were found in the tumor area. After the injection of adenovirus carrying the LacZ gene into the hepatic artery, the selective expression of transgene in the tumor cell was achieved. These findings indicate that the HSV-tk/GCV strategy, using an adenoviral vector, could be a promising avenue for the treatment of hepatocellular carcinoma.

Immunological characterization of a mucin-associated protein from hamster tracheal epithelial cell culture

Airway mucins are high molecular mass (>10(6) dalton) glycoproteins with various types of associated molecules including glycoproteins, lipoproteins, and lipids. The study of mucin-associated proteins is limited largely due to the lack of specific probes. In this study, we produced a monoclonal antibody, MAbHT10, against a 190-kDa mucin associated-protein by immunizing mice with hamster airway mucin purified in nondissociative condition. Using HT10, the 190-kDa mucin-associated protein was characterized immunologically. The 190-kDa mucin-associated protein is glycoprotein and HT10 recognized carbohydrate containing portion of the protein. The association of 190-kDa protein with mucin is strong enough that heat and detergent treatment is required to dissociate it from mucin as evidenced by gel filtration chromatography, Western blot, enzyme-linked immunoadsorbent assay (ELISA), and co-immunoprecipitation. The expression of the 190-kDa protein is increased with the development of hamster tracheal epithelial cells in culture, but showed differences with the pattern of the regulation of mucin expression. Adenosine triphosphate (ATP), a known strong mucin secretagogue, dose-dependently increased mucin release but caused only marginal increase in the release of the 190-kDa protein. The MAb should be useful in the structural and functional analysis of the 190-kDa mucin-associated proteins in physiological and pathological situations such as chronic airway diseases.

ATP-induced mucin release from cultured airway goblet cell involves, in part, activation of phospholipase A2

Adenosine triphosphate (ATP) has been shown to stimulate mucin release by activation of protein kinase C (PKC) following activation of phospholipase C (PLC) coupled to the P2 receptor via G-proteins. The aim of the present study was to investigate pathways downstream to the PKC activation in ATP-induced mucin release from primary hamster tracheal surface epithelial (HTSE) cells. The release of mucin was determined by chromatographic procedure after metabolic labeling of mucin with [3H]-glucosamine. The results were: i) ATP induced the release of arachidonic acid, which caused the release of mucin. Pretreatment with mepacrine (0.3 mM), a phospholipase A2 (PLA2) inhibitor, inhibited the ATP-induced arachidonic acid and mucin release. Oleoyloxyethylphosphocholine, another PLA2 inhibitor, gave similar results. ii) An activator of PKC, 4 beta-phorbol-12 alpha-myristate-13-acetate (PMA, 1 microM) induced mucin release, which was inhibited by mepacrine pretreatment. iii) Downregulation of PKC by prolonged (16 h) PMA treatment caused inhibition of ATP-induced mucin release. Treatment of PKC downregulated HTSE cells with mepacrine did not further decrease the ATP-induced mucin release. These results suggest that PLA2 is involved in ATP-induced mucin release and its activation is sequential to the PLC-PKC pathway.

The growth inhibition of hepatoma by gene transfer of antisense vascular endothelial growth factor

BACKGROUND

Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis and tumor growth in solid tumors. Therefore, to induce tumor regression, antiangiogenic agents to block VEGF need to be administered repeatedly.

METHOD

We constructed the recombinant mammalian expression vector bearing an antisense-VEGF cDNA, pZeoVEGFa. We examined the effect of pZeoVEGFa on the growth of SK-HEP1 hepatoma cells, bovine capillary endothelial (BCE) cells, and tubule formation of BCE cells in fibrin gel. To evaluate the function of pZeoVEGFa in vivo, we implanted SK-HEP1 hepatoma cells subcutaneously into nude mice.

RESULTS

In SK-HEP1 hepatoma cells, we showed that the synthesis of VEGF protein was suppressed by the stable and transient transfection of pZeoVEGFa. pZeoVEGFa inhibited the proliferation of BCE cells and significantly suppressed tubule formation of BCE cells. pZeoVEGFa inhibited a morphological change from a round shape to an elongated spindle shape in fibrin gel. When pZeoVEGFa was injected peritumorally by liposomes, tumor growth was inhibited.

CONCLUSION

Endothelial cell proliferation, tubule formation and tumor growth may be diminished by down-regulation of endogenous VEGF expression in tumor cells or tissue. These findings indicate that the efficient down-regulation of the VEGF produced by tumor cells using antisense strategies has an antitumor effect. We suggest that VEGF-targeted antiangiogenic gene therapy could be an effective strategy to treat VEGF-producing tumors.

Muc1 mucins on the cell surface are adhesion sites for Pseudomonas aeruginosa

Recently, we cloned and characterized a full-length cDNA of the hamster Muc1 gene, the expression of which appears to be associated with secretory cell differentiation (Park HR, Hyun SW, and Kim KC. Am J Respir Cell Mol Biol 15: 237-244, 1996). The role of Muc1 mucins in the airway, however, is unknown. In this study, we investigated whether cell surface mucins are adhesion sites for Pseudomonas aeruginosa. Chinese hamster ovary (CHO) cells not normally expressing Muc1 mucin were stably transfected with the hamster Muc1 cDNA, and binding to P. aeruginosa was examined. Our results showed that 1) stably transfected CHO cells expressed both Muc1 mRNA and Muc1 mucins based on Northern and Western blot analyses, 2) Muc1 mucins present on the cell surface were degraded by neutrophil elastase, and 3) expression of Muc1 mucins on the cell surface resulted in a significant increase in adhesion of P. aeruginosa that was completely abolished by either proteolytic cleavage with neutrophil elastase or deletion of the extracellular domain by mutation. We conclude that Muc1 mucins expressed on the surface of CHO cells serve as adhesion sites for P. aeruginosa, suggesting a possible role for these glycoproteins in the early stage of airway infection and providing a model system for studying epithelial cell responses to bacterial adhesion that leads to airway inflammation in general and cystic fibrosis in particular.

Broad bean wilt virus Causes Necrotic Symptoms and Generates Defective RNAs in Capsicum annuum

ABSTRACT A virus was isolated from hot pepper (Capsicum annuum cv. Hyang Chon) growing in Korea and displaying necrotic spots or streaks on leaves and stems followed by stunting and death of plants. Morphological and host range analyses of extracts from infected plants suggested that the causal agent of disease was a Broad bean wilt virus (BBWV), and the virus was tentatively named a Korean isolate of BBWV (BBWV-K). When the isolate was back-inoculated onto hot pepper plants, it induced symptoms similar to those of naturally infected hot pepper in the field. Two coat proteins (CPs) of 44 and 22 kDa, corresponding to a large CP and a small CP, respectively, were identified from the virus, and both reacted specifically with polyclonal antibody to BBWV 2. The complete nucleotide sequences of RNA 1 and RNA 2 of the isolate were determined from cDNA clones. The deduced amino acid sequence data from the putative proteins encoded by RNA 1 and 2 of the BBWV-K indicated a closer relationship with the isolates of BBWV 2 than BBWV 1. However, sequence comparison of the 5' noncoding regions of the viruses differentiates BBWV-K from other BBWV 2 isolates. Another distinctive feature of the BBWV-K is that it generates defective RNAs in hot pepper exhibiting necrotic symptoms, which is the first report of defective RNAs in the Fabavirus genera of BBWVs.

Taming superacids: stabilization of the fullerene cations HC60+ and C60.+

A new superacid, H(CB11H6X6) (where X = chlorine or bromine), whose conjugate base is the exceptionally inert CB11H6X6- carborane anion, separates Bronsted acidity from oxidizing capacity and anion nucleophilicity in a manner not previously achieved. Reaction of this superacid with C60 gives HC60+ as a stable ion in solution and in the solid state. In a separate experiment, an oxidant was developed such that the long-sought C60.+ ion can be synthesized in solution. The preparation of these two fullerene carbocations is a notable departure from the prevalent chemistry of C60, which is dominated by the formation of anions or the addition of nucleophiles. The H(CB11H6X6) superacid overcomes the major limitations of presently known superacids and has potentially wide application.

The growth inhibition of hepatoma by gene transfer of antisense vascular endothelial growth factor

BACKGROUND

Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis and tumor growth in solid tumors. Therefore, to induce tumor regression, antiangiogenic agents to block VEGF need to be administered repeatedly.

METHOD

We constructed the recombinant mammalian expression vector bearing an antisense-VEGF cDNA, pZeoVEGFa. We examined the effect of pZeoVEGFa on the growth of SK-HEP1 hepatoma cells, bovine capillary endothelial (BCE) cells, and tubule formation of BCE cells in fibrin gel. To evaluate the function of pZeoVEGFa in vivo, we implanted SK-HEP1 hepatoma cells subcutaneously into nude mice.

RESULTS

In SK-HEP1 hepatoma cells, we showed that the synthesis of VEGF protein was suppressed by the stable and transient transfection of pZeoVEGFa. pZeoVEGFa inhibited the proliferation of BCE cells and significantly suppressed tubule formation of BCE cells. pZeoVEGFa inhibited a morphological change from a round shape to an elongated spindle shape in fibrin gel. When pZeoVEGFa was injected peritumorally by liposomes, tumor growth was inhibited.

CONCLUSION

Endothelial cell proliferation, tubule formation and tumor growth may be diminished by down-regulation of endogenous VEGF expression in tumor cells or tissue. These findings indicate that the efficient down-regulation of the VEGF produced by tumor cells using antisense strategies has an antitumor effect. We suggest that VEGF-targeted antiangiogenic gene therapy could be an effective strategy to treat VEGF-producing tumors.

Organo-axial volvulus of the stomach with diaphragmatic eventration

Gastric volvulus occurs when the stomach rotates about its longitudinal axis (organo-axial volvulus), or about an axis joining the lesser and greater curvatures (mesentero-axial volvulus). Primary gastric volvulus, making up one third of cases, occurs when the stabilizing ligaments are too lax as a result of congenital or acquired causes. Secondary gastric volvulus, making up the remainder of cases, occurs in association with a paraesophageal hernia or other congenital or acquired diaphragmatic defects. While gastric volvulus may occur acutely, especially in children, it may not be clinically apparent and discovered incidentally. The authors present a case of chronic organo-axial volvulus of the stomach secondary to left hemidiaphragmatic eventration with a review of the relevant literature.

FGFR3 gene mutation (Gly380Arg) with achondroplasia and i(21q) Down syndrome: phenotype-genotype correlation

We report the case of a boy with achondroplasia and i(21q) Down syndrome. Besides craniofacial features typical in Down syndrome, the skeletal findings of achondroplasia dominate the clinical picture. The diagnosis of Down syndrome was based on clinical features and the cytogenetic finding of i(21q) trisomy 21. The diagnosis of achondroplasia was based on the presence of clinical and radiographic findings and confirmed by the presence of a common FGFR3 gene mutation (Gly380Arg) detected by restriction enzyme analysis and sequencing of the polymerase chain reaction products. This is the first report of achondroplasia associated with i(21q) Down syndrome.

Squamous differentiation downregulates Muc1 mucin in hamster tracheal surface epithelial cell

To investigate whether the squamous differentiation of primary hamster tracheal epithelial cell, which is induced by retinoic acid deficiency or chronic PMA treatment, regulates Muc1 expression, we first produced and characterized a monoclonal antibody against hamster tracheal Muc1 mucin using pGEX-Muc1 fusion protein as an antigen and the changes of Muc1 mucin expression was determined by Western blot. Squamous differentiation downregulated the expression of Muc1 mucin from HTSE cells. The decrease in the immunoreactivity of Muc1 mucin was parallel to the decrease in the immunoreactivity of high molecular weight mucin, which is secreted from HTSE cells. The data from the present study implicate a possible role of Muc1 mucin in squamous differentiation of HTSE cells.

Androgen receptor gene mutation identified by PCR-SSCP and sequencing in 4 patients with complete androgen insensitivity syndrome

To study the genetic defect of the human androgen receptor (hAR) gene in the complete androgen insensitivity syndrome (CAIS), we amplified each of the eight exons by PCR in genomic DNA extracted from the paraffin blocks of the resected gonads. We analyzed using SSCP, and directly sequenced the abnormally shifted bands. Mutations were found in 4 cases of CAIS. Patient 1 carried a point mutation; a G to A transition in exon 7 resulted in a change from arginine to glutamine at codon 831. Patient 2 carried a point mutation; a C to T transition in exon 7 resulted in a change from arginine to stop at codon 831. Patient 3 carried a point mutation and deletion in exon 7. A point mutation was an A to G transition that caused a glutamine to be substituted for the asparagine present at codon 819. A deletion of a G at codon 820 resulted in a frameshift and consequently in the introduction of a premature stop at codon 821. Patient 4 carried a mutation in 5' splice donor site of intron 7; a G to T transition might have caused an abnormal splicing of the exon 7. All of the mutations were found in exon 7. These mutations of hAR gene might be related to the pathogenesis of CAIS.

Construction and characterization of a chimeric receptor containing the cytoplasmic domain of MUC1 mucin

MUC1 mucin is a transmembrane glycoprotein that is highly expressed in various cancer cell lines and is also present in most of the glandular epithelial cells including the airway. Although the presence of numerous phosphorylation sites in its cytoplasmic domain suggests its potential role as a receptor, the unavailability of a ligand for MUC1 mucin has limited our understanding of its function. In this paper, we tried to circumvent this problem by constructing a chimeric receptor containing the cytoplasmic domain of MUC1 mucin, which can be phosphorylated on activation. To this end, we constructed a chimeric plasmid vector (pCD8/MUC1) by replacing the extracellular and transmembrane domains of human MUC1 mucin with those of human CD8. Transient transfection of the vector into COS-7 cells resulted in expression of the chimeric receptor on the surface of the COS-7 cells as judged by immunologic assays with various antibodies as well as by fluorescence-activated cell-sorting analysis. Treatment of the transfected COS-7 cells with an anti-CD8 antibody resulted in a significant increase in phosphorylation of tyrosine moieties of the chimeric receptor. This chimeric receptor will serve as a powerful tool in elucidating the signaling mechanism as well as the functional role of MUC1 mucin in the airway.

Inhaled ATP causes mucin release from goblet cells of intact rats

Secretion of mucins from airway epithelial cells has been studied almost exclusively using in vitro cell culture systems. Our understanding of in vivo secretion is greatly limited due to the unavailability of both suitable model systems and adequate assays. It has been reported that ATP induces mucin release from the cultured primary tracheal surface epithelial cell, but there is no clear demonstration of the effect of ATP on mucin release in vivo, which is important to understand the mechanism of mucin release in vivo and also to devise means for regulation of mucin release. The objective of this experiment was to see if inhaled ATP could stimulate airway mucin release in intact rats using both enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. The results were: (1) a new monoclonal antibody (mAbRT03) developed against purified rat mucins specifically recognized high-molecular-mass mucins; (2) ELISA results with conventional gel-filtration assay results are virtually superimposable; (3) inhalation of ATP in intact rats resulted in a dose-independent increase in the amount of mucins in the tracheal lavage fluid with a concomitant decrease in the number of mucin-positive cells in the trachea. We conclude that extracellular ATP can stimulate mucin release from the airway in vivo, and the present rat inhalation system combined with ELISA of the airway secretions should serve a useful model for studying the pharmacology of airway mucin secretion in vivo.

Nucleotide-induced PMN adhesion to cultured epithelial cells: possible role of MUC1 mucin

Accumulation of intraluminal polymorphonuclear leukocytes (PMN) is a hallmark of inflammatory diseases of the airways. Extracellular nucleotides stimulate PMN adhesion to human main pulmonary artery endothelial cells (HPAEC) by a purinoceptor-mediated mechanism. We investigated the effects of nucleotides on adhesion of freshly isolated human PMN to cultured human tracheobronchial epithelial cells (HBEC). We found that extracellular ATP and UTP were much less effective in stimulating PMN adhesion to HBEC compared with HPAEC, whereas the bacterial chemotactic peptide N-formyl-Met-Leu-Phe stimulated PMN adhesion to both cell types to an equal degree. We investigated several mechanisms that might account for decreased nucleotide-induced PMN adhesion to HBEC. The ectonucleotidase-resistant ATP analog adenosine 5'-O-(3-thiotriphosphate) was also ineffective in stimulating PMN adhesion to HBEC, indicating that degradation of ATP by ectonucleotidase(s) was not responsible for altered PMN adhesion. HBEC responded to ATP and UTP with increased intracellular calcium, indicating that these cells are capable of purinoceptor-mediated responses. We found that ATP and UTP also did not stimulate PMN adhesion to Chinese hamster ovary (CHO) cells, which had been stably transfected with the gene for hamster Muc1, a cell-associated mucin. However, ATP and UTP did stimulate adhesion of PMN to nontransfected CHO cells. These results suggested that MUC1 mucin modulates PMN adhesion to epithelium. We found that cultured HBEC expressed more mRNA and protein for MUC1 mucin than did HPAEC. We conclude that extracellular nucleotides are less effective in stimulating PMN adhesion to epithelial cells than to endothelial cells and that overexpression of hamster Muc1 mucin inhibits nucleotide-induced PMN adhesion to CHO cells.

Inhibition of mucin release from airway goblet cells by polycationic peptides

In the present study, we investigated whether polycationic peptides affect mucin release from cultured airway goblet cells. Confluent primary hamster tracheal surface epithelial cells were metabolically radiolabeled with [(3)H]glucosamine for 24 h and chased for 30 min in the presence of varying concentrations of either poly-L-arginine (PLA) or poly-L-lysine (PLL) to assess the effects on [(3)H]mucin release. Possible cytotoxicity by the polycations was assessed by measuring lactate dehydrogenase release, (51)Cr release, and cell exfoliation. The results were as follows: 1) both PLA and PLL inhibited mucin release in a dose-dependent fashion; 2) there was no significant difference in either lactate dehydrogenase release, (51)Cr release, or the number of floating cells between control and treatment groups; 3) the effects of both PLA and PLL on mucin release were completely blocked by neutralizing the positive charges either by pretreatment with heparin or by N-acetylation of the polycations; and 4) both PLA and PLL completely masked the stimulatory effect of ATP on mucin release. We conclude that these polycationic peptides can inhibit mucin release from airway goblet cells without any apparent cytotoxicity, and the inhibitory effect seems to be attributable to their positive charges. These are the first nonsteroidal agents, to the best of our knowledge, that have been shown to inhibit mucin release from airway goblet cells.

A monoclonal antibody against hamster tracheal mucin, which recognizes N-acetyl-galactosamine containing carbohydrate chains as an epitope

Airway mucin that is present in airway secretion, plays an important role in host-defense by trapping airborne particles and removing them by mucociliary transport system. For the study of mucin, it is crucially important to have antibodies specific against mucin because other commonly used methods such as histologic stain for the detection of mucin usually suffer from varying levels of nonspecificity. In this study, we produced a monoclonal antibody (MAb) against hamster airway mucin, which is one of the most commonly used animal species for the study of mucin in vitro, and characterized its immunological properties along with the determination of the epitope it recognizes. The MAb, which was named MAb HTA, was IgM isotype and specific against mucin from both in vitro cell culture and in vivo airway secretion. In Western blot, MAb HTA specifically recognized high molecular weight airway mucin, which was also confirmed by the appearance of peak profile of immunological signal only on void volume fraction in Sepharose CL-4B gel filtration chromatography. It also immunoprecipitated high molecular weight hamster airway mucin with the aid of antimouse IgM agarose. In immunohistochemical stain of hamster trachea, it showed strong signal on airway epithelium and also on the mucin secreting goblet cell granules. The immunological signal was greatly increased by the treatment of endotoxin, which has been reported to cause airway secretory cell metaplasia. The MAb HTA recognized carbohydrate chains containing N-acetyl-galactosamine, one of the linking sugars of airway mucin, as an epitope. Treatment of mucin with N-acetyl-galactosaminidase caused great reduction of immunological signal. To the best of our knowledge, this is the first to report a MAb that recognizes N-acetylgalactosamine, a linking sugar of airway mucin. The specificity of MAb HTA against airway mucin and the clear demonstration of the epitope it recognizes should greatly aid the pharmacological and biochemical study of mucin in various physiological and pathological situations.

Ganoderma lucidum extract protects DNA from strand breakage caused by hydroxyl radical and UV irradiation

The fruit bodies of Ganoderma lucidum have been used for the prevention and treatment of various diseases in the Orient. Its antitumor and immune enhancing properties, along with no cytotoxicity, raise the possibility that it could be effective in preventing oxidative damage and resulting disease. Using agarose gel electrophoresis, we have evaluated the potential of Ganoderma lucidum extract as a radioprotector and antioxidant defense against oxygen radical-mediated damage. Although the evidence presented here is based on in vitro using isolated DNA, the results clearly demonstrate that the hot-water extract of Ganoderma lucidum shows good radioprotective ability, as well as protection against DNA damage induced by metal-catalyzed Fenton reactions and UV irradiation. We also found that the water-soluble polysaccharide isolated from the fruit body of Ganoderma lucidum was as effective as the hot-water extract in protecting against hydroxyl radical-induced DNA strand breaks, indicating that the polysaccharide compound is associated with the protective properties. Our data suggest that Ganoderma mushroom merits investigation as a potential preventive agent in humans.

Noradrenaline synchronizes evoked quantal release at frog neuromuscular junctions

1. Noradrenaline (NA) increases synaptic efficacy at the frog neuromuscular junction. To test the hypothesis that one of the actions of NA is to shorten the period over which evoked quanta are released, we measured the latencies of focally recorded uniquantal endplate currents (EPCs). 2. NA shortened the release period for evoked quantal release. The interval between the time when responses with minimal delay appeared and the point at which 90 % of all latencies had occurred was shortened in the presence of 1 x 10-5 M NA by about 35 % at 20 C and by about 45 % at 8 C. Inhibitor and agonist experiments showed that NA acts on a beta-adrenoreceptor. 3. The better synchronization of release significantly increased the size of reconstructed multi- quantal EPCs. This suggests that NA facilitates synaptic transmission by making the release of quanta more synchronous. 4. The synchronizing action of NA might potentiate neuromuscular transmission during nerve regeneration, transmitter exhaustion and other extreme physiological states where the quantal content is reduced, such as survival in cold and hibernation.