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Effect of tetrodotoxin on membrane potentials and active tone in vascular smooth muscle
STOLC, V. (Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A .) Stimulation of adenosine 3',5'-monophosphate formation in mononuclear leukocytes by toad venoms . Bioch&n. biophys. Acts 721, 236 (1982). THE coNTENT of adenosine 3',5'-monophosphate in human mononuclear leukocytes was enhanced 3-5-times by venoms obtained from African toad (Bufo gfricanus), American toad (Bufo amerlcanus), Colorado river toad (Bgfo arenarum) and marine toad (Bufo marinus) at 25 Mg/ml for 5 min incubation at 37°C . The maximum stimulation was observed after 1- 5 min incubation . The half-maximal stimulation was observed at 0.1 k8/ml venom obtained from Colorado river toad (Bt(fo arenarum) . The increased content of adenosine 3',5'monophosphate in the mononuclear leukocytes persisted without significant change for at least 30 min incubation at 37°C . H. P. KOLM ROBB, J., KIRKPATRICK, K. S. and NORVAL, M. (East of Scotland College of Agriculture, Edinburgh, U.K .) Association of toxin-producing fungi with disease in broilers. Vet. Rec. 111, 389 (1982) . AN EPISODE of suboptimal growth, poor feathering and behavioural abnormalities in broilers in Scotland during the winter of 1980-81 is described. This was considered to be associated with mould-contaminated maize and wheat components of the feed, from which fusaria were isolated in persistently high numbers. Four species, Fusarium culmorum, F. tricincturn, F. nivale and F. monil(forme, were identified . Specific identification by thin layer chromatography of the mycotoxins deoxynivalenol, zearalenone and diacetoxyscirpenol was achieved in some extracts . In addition, several other areas of the chromatograms were found to be toxic in the HEp II all system and these may contain toxins for which standards were not available or, alternatively, previously uncharacterised fungal metabolites. H. P. KOLM RABA, R. and AAviKSAAR, A. (Institute of Chemical Physics and Biophysics of the Academy of Sciences of the Estonian SSR, Biochemistry Department, Tallinn, U.S.S.R .) Cobra venom acetylcholinesterase : nature of charge isoforms . Eur. J. Blochern. 127, 507 (1982). CHARGE isoforms of cobra (Ngja nqja oxiana) venom acetylcholinesterase, separated by isoelectric focusing, differ only by the number of free carboxyl groups of glutamic and/or aspartic acid side-chains in the enzyme molecule . The isoforms appear to be produced by a post-translational deamidation of accessible glutamin and/ or asparagine residues . The isoforms have identical catalytic specificities towards characteristic acetylcholinesterase substrates . H. P. KOLM RISK, M., NORRIS, P. J., CouTmHo-Nm-ro, J. and BRADFORD, H. F. (Department of Biochemistry, Imperial College of Science and Technology, London, U.K ., and Hypertension, Endocrinology Division, University of Texas, Galveston, Texas, U.S .A.) Actions of Ptychodiscus brevis red tide toxin on metabolic and transmitterreleasing properties of synaptosomes . J. Neurochem. 39, 1485 (1982) .
A PURE toxin isolated from Ptychodiwus brevis stimulated differential release of amino acid neurotransmi tters from mammalian cortical synaptosomes together with loss of K` content and respiratory stimulation at 40 ng/ml. The effect was blocked by tetrodotoxin and by verapamil, implicating Na' channel activation and possibly Cap' influx as necessary for the response, although the response did not change upon omission of Ca'* . Verapamil was therefore likely to be acting as a Na' channel blocker in this instance . The toxin at 40 ng/ml caused acetylcholine release from guinea pig ileum, which is consistent with the proposed depolarising action for the toxin. H. P. KOLM KAwAI, N., NiwA, A. and ABE, T. (Department of Neurobiology, Tokyo Metropolitan Institute for Neurosciences, 2-6, Musashidal, Fuchu-City, Tokyo 183, and (T .A .) Laboratory of Insect Toxicology, Institute of Physical and Chemical Research, Wako-City, Saltama 351, Japan) Spider venom contains specific receptor blocker of glutaminergic synapses . Brain Res. 247, 169 (1982) . EFFECTS of a toxin separated from a spider (Nephila clavata) venom on glutaminergic synapses were studied using lobster neuromuscular junctions. The spider toxin selectively and irreversibly blocked excitatory postsynaptic potentials without affecting the inhibitory postsynaptic potentials . The toxin had no effect on the nerve terminal spikes nor on the resting membrane conductance. Glutamate potential in the postsynaptic membrane was abolished by the toxin, but aspartate-induced depolarization was unaffected . H. P. KoLM LOMBARD, J. H., BuRKE, M. J., CONTNEY, S. J., WILLEMS, W. J. and STEKiEL, W. J. (Department of Physiology, The Medical College of Wisconsin, Milwaukee, Wisconsin 53226, U.S .A .) Effect of tetrodotoxin on
994
Reviews
membrane potentials and active tone in vascular smooth muscle. Am. J.
PhysioL 242,
H967 (1982) .
THE SUITABILITY of tetrodotoxin (TTX) for studies of the neural control of vascular smooth muscle (VSM) tone in the microcirculation was evaluated by determining : (1) whether TTX blockade of neural input to adrenergically innervated VSM is reversible ; (2) whether TTX depresses active VSM tone directly. Diameters of rat mesenteric veins and third- and fourth-order arterioles of the hamster cheek pouch were measured by image splitting. VSM transmembrane potentials (E,) were measured with microelectrodes in rat meseenteric veins. In the veins, TTX suffusion (10-" g/ml) resulted in dilation and reversible F, hyperpolarization . TTX also reversibly blocked the venoconstrictor response to perivascular nerve stimulation . TTX had no effect on the resting tone of hamster arterioles or on arteriolar constriction in response to increased oxygen availability . TTX did not affect the response to norepinephrine in either-preparation . This study indicates that TTX specifically and reversibly blocks VSM responses to neural activation, but that it has no direct depressant effect on resting VSM tone or active constriction in response to non-neural activation . H. P. KOLM WILLIAMS, J. A., GALLAGHER, S. and SANKARAN, H. (Cell Biology Research Laboratory, Harold Brunn Research Institute, Department of Medicine, Mount Zion Hospital and Medical Center, San Francisco, California 94120, and Department of Physiology-University of California, San Francisco, California 94143, U.S .A .) Scorpion toxin-induced amylase secretion in guinea pig pancreas : evidence for a new neurotransmitter . Proc . Soc. exp. BioL Med. 170, 384 (1982) . SCORPION toxin, a substance that induces neurotransmitter release by depolarizing neurons, was used to stimulate amylase release from guinea pig pancreatic lobules. Scorpion toxin was found to act selectively on acinar cell neurons, but not directly on acinar cells. The toxin's action on lobules was blocked by tetrodotoxin, whereas scorpion toxin itself had no effect on isolated pancreatic acini. Toxin-induced amylase secretion from pancreatic lobulesincluded two components, one that was atropine sensitive and one that was atropine resistant . This finding is consistent with the notion that scorpion toxin releases cholinergic and noncholinergic transmitters . Both cholinergic and noncholinergic effects showed a similar dose dependence, being maximal at a toxin concentration of 3 jug/ml. The noncholinergic pathway was notmediated through the CCK receptor, since it was not blocked by dibutyryl cyclic GMP, a CCK antagonist . Moreover, the noncholinergic mechanism appeared to have a different biochemical mechanism of action than CCK, in that scorpion toxin in the presence of atropine did not rapidly release intracellular Ca" pretabeled with "Ca" . The results suggest, therefore, the existence of a second neurotransmitter present in pancreatic nerve endings capable of stimulating amylase release in the guinea pig. H. P. KOLM DUNN, I. S., LIBERATo, D. J., CASTAGNOLI, N. and BYERS, V. S. (Department of Dermatology and Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, U.S .A .) Suppression of contact sensitivity in mice by cutaneous application of a poison ivy urushiol analogue . Ann. N. Y. Acad. Sci. 392, 385 (1982) . ABDOMINAL painting of mice with 3-heptadecylcatechol (HDC) or 3-pentadecylcatechol (PDC) (components of poison oak and ivy urushiol oils, respectively) results in contact sensitization with characteristics of delayed-type hypersensitivity . Neither the corresponding 4-methyl or 6-methyl PDC derivatives produced significant suppression; only the 4-methyl compound produced enhancement of sensitization to the second treatment with HDC. Lymph node cells taken from mice ten days after treatment with 5-Me-PDC, but not PDC, depressed the induction of PDC sensitization when transferred into normal recipients . These results suggest that cutaneous treatment of mice with 5-Me-PDC induces a cellular population with suppressive activity against the induction of HDC or PDC sensitization andthat the suppression is related to the blocking of specific covalent binding sites on the catechol ring . H. P. KoLM WALzEL, H., Mix, E., JENssEN, H.-L., ZISKA, P. and FRANz, H. (Universität Rostock, Bereich Medizin, Abteilung Neurologie, Forschungsgruppe Neuro- und Tumorimmunologie, Rostock, and Staatliches Institut für Immunpräparate und Nährmedien, Berlin, G.D.R .) Estimation of toxicity of the mistletoe lectin 1 using the footpad swelling test in mice . Acta histochem. 71, 41 (1982) . Mistletoe lectin 1 causes footpad swelling at a dose ;o 0.025 Mg per mouse. Dose dependence and kinetics of the reaction have been measured . H. P. KoLM BARHANIN, J., GIOLIO, J. R., LáoPOLD, P., SCHMm, A., SAMPAIO, S. V. and LAZDuNsvi, M. (Centre de Biochimie du Centre National de la Recherche Scientifique, Université de Nice, 06034 Nice, France, and Universidade de Sao Paulo, Faculdade de Medicina de Ribeirao Preto, 14100 Ribeirao Preto, Sao Paulo, Brazil)
A PURE toxin isolated from Ptychodiwus brevis stimulated differential release of amino acid neurotransmi tters from mammalian cortical synaptosomes together with loss of K` content and respiratory stimulation at 40 ng/ml. The effect was blocked by tetrodotoxin and by verapamil, implicating Na' channel activation and possibly Cap' influx as necessary for the response, although the response did not change upon omission of Ca'* . Verapamil was therefore likely to be acting as a Na' channel blocker in this instance . The toxin at 40 ng/ml caused acetylcholine release from guinea pig ileum, which is consistent with the proposed depolarising action for the toxin. H. P. KOLM KAwAI, N., NiwA, A. and ABE, T. (Department of Neurobiology, Tokyo Metropolitan Institute for Neurosciences, 2-6, Musashidal, Fuchu-City, Tokyo 183, and (T .A .) Laboratory of Insect Toxicology, Institute of Physical and Chemical Research, Wako-City, Saltama 351, Japan) Spider venom contains specific receptor blocker of glutaminergic synapses . Brain Res. 247, 169 (1982) . EFFECTS of a toxin separated from a spider (Nephila clavata) venom on glutaminergic synapses were studied using lobster neuromuscular junctions. The spider toxin selectively and irreversibly blocked excitatory postsynaptic potentials without affecting the inhibitory postsynaptic potentials . The toxin had no effect on the nerve terminal spikes nor on the resting membrane conductance. Glutamate potential in the postsynaptic membrane was abolished by the toxin, but aspartate-induced depolarization was unaffected . H. P. KoLM LOMBARD, J. H., BuRKE, M. J., CONTNEY, S. J., WILLEMS, W. J. and STEKiEL, W. J. (Department of Physiology, The Medical College of Wisconsin, Milwaukee, Wisconsin 53226, U.S .A .) Effect of tetrodotoxin on
994
Reviews
membrane potentials and active tone in vascular smooth muscle. Am. J.
PhysioL 242,
H967 (1982) .
THE SUITABILITY of tetrodotoxin (TTX) for studies of the neural control of vascular smooth muscle (VSM) tone in the microcirculation was evaluated by determining : (1) whether TTX blockade of neural input to adrenergically innervated VSM is reversible ; (2) whether TTX depresses active VSM tone directly. Diameters of rat mesenteric veins and third- and fourth-order arterioles of the hamster cheek pouch were measured by image splitting. VSM transmembrane potentials (E,) were measured with microelectrodes in rat meseenteric veins. In the veins, TTX suffusion (10-" g/ml) resulted in dilation and reversible F, hyperpolarization . TTX also reversibly blocked the venoconstrictor response to perivascular nerve stimulation . TTX had no effect on the resting tone of hamster arterioles or on arteriolar constriction in response to increased oxygen availability . TTX did not affect the response to norepinephrine in either-preparation . This study indicates that TTX specifically and reversibly blocks VSM responses to neural activation, but that it has no direct depressant effect on resting VSM tone or active constriction in response to non-neural activation . H. P. KOLM WILLIAMS, J. A., GALLAGHER, S. and SANKARAN, H. (Cell Biology Research Laboratory, Harold Brunn Research Institute, Department of Medicine, Mount Zion Hospital and Medical Center, San Francisco, California 94120, and Department of Physiology-University of California, San Francisco, California 94143, U.S .A .) Scorpion toxin-induced amylase secretion in guinea pig pancreas : evidence for a new neurotransmitter . Proc . Soc. exp. BioL Med. 170, 384 (1982) . SCORPION toxin, a substance that induces neurotransmitter release by depolarizing neurons, was used to stimulate amylase release from guinea pig pancreatic lobules. Scorpion toxin was found to act selectively on acinar cell neurons, but not directly on acinar cells. The toxin's action on lobules was blocked by tetrodotoxin, whereas scorpion toxin itself had no effect on isolated pancreatic acini. Toxin-induced amylase secretion from pancreatic lobulesincluded two components, one that was atropine sensitive and one that was atropine resistant . This finding is consistent with the notion that scorpion toxin releases cholinergic and noncholinergic transmitters . Both cholinergic and noncholinergic effects showed a similar dose dependence, being maximal at a toxin concentration of 3 jug/ml. The noncholinergic pathway was notmediated through the CCK receptor, since it was not blocked by dibutyryl cyclic GMP, a CCK antagonist . Moreover, the noncholinergic mechanism appeared to have a different biochemical mechanism of action than CCK, in that scorpion toxin in the presence of atropine did not rapidly release intracellular Ca" pretabeled with "Ca" . The results suggest, therefore, the existence of a second neurotransmitter present in pancreatic nerve endings capable of stimulating amylase release in the guinea pig. H. P. KOLM DUNN, I. S., LIBERATo, D. J., CASTAGNOLI, N. and BYERS, V. S. (Department of Dermatology and Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, U.S .A .) Suppression of contact sensitivity in mice by cutaneous application of a poison ivy urushiol analogue . Ann. N. Y. Acad. Sci. 392, 385 (1982) . ABDOMINAL painting of mice with 3-heptadecylcatechol (HDC) or 3-pentadecylcatechol (PDC) (components of poison oak and ivy urushiol oils, respectively) results in contact sensitization with characteristics of delayed-type hypersensitivity . Neither the corresponding 4-methyl or 6-methyl PDC derivatives produced significant suppression; only the 4-methyl compound produced enhancement of sensitization to the second treatment with HDC. Lymph node cells taken from mice ten days after treatment with 5-Me-PDC, but not PDC, depressed the induction of PDC sensitization when transferred into normal recipients . These results suggest that cutaneous treatment of mice with 5-Me-PDC induces a cellular population with suppressive activity against the induction of HDC or PDC sensitization andthat the suppression is related to the blocking of specific covalent binding sites on the catechol ring . H. P. KoLM WALzEL, H., Mix, E., JENssEN, H.-L., ZISKA, P. and FRANz, H. (Universität Rostock, Bereich Medizin, Abteilung Neurologie, Forschungsgruppe Neuro- und Tumorimmunologie, Rostock, and Staatliches Institut für Immunpräparate und Nährmedien, Berlin, G.D.R .) Estimation of toxicity of the mistletoe lectin 1 using the footpad swelling test in mice . Acta histochem. 71, 41 (1982) . Mistletoe lectin 1 causes footpad swelling at a dose ;o 0.025 Mg per mouse. Dose dependence and kinetics of the reaction have been measured . H. P. KoLM BARHANIN, J., GIOLIO, J. R., LáoPOLD, P., SCHMm, A., SAMPAIO, S. V. and LAZDuNsvi, M. (Centre de Biochimie du Centre National de la Recherche Scientifique, Université de Nice, 06034 Nice, France, and Universidade de Sao Paulo, Faculdade de Medicina de Ribeirao Preto, 14100 Ribeirao Preto, Sao Paulo, Brazil)