Analysis of Slow Hyperpolarizing Potentials in Frog Taste Cells Induced by Glossopharyngeal Nerve Stimulation

Chemical Senses, 29,     

Characterization and purification of polymorphic arylalkylamine N-acetyltransferase from the American cockroach, Periplaneta americana.

We separated two forms of arylalkylamine N-acetyltransferase (AANAT) from various organs of the American cockroach, Periplaneta americana. Both forms of the enzyme had an equivalent molecular mass of 28 kDa. One form isolated from the testicular accessory glands had high enzyme activity at acidic pHs. The isoelectric point was 5-6 and the substrate specificity was wider than the other type. The other isolated form from female midguts had a higher level of enzyme activity at basic pHs. These findings suggested that P. americana contains polymorphic AANAT, as is the case in Drosophila melanogaster. These forms differed not only in pH specificity, and substrate specificity but in chromatographic behavior and kinetic properties. Most of the organs we examined contained a mixture of the two forms since two types of AANAT activity were separated in different chromatographic fractions when two pH conditions were used for activity measurement.     

Arterial perfusion of frog tongue for intracellular recording of taste cell receptor potential

The frog tongue was perfused through its artery with a Ringer solution using a peristaltic pump, and a method was developed to record stable intracellular receptor potentials of taste cells. Perfusing at 0.05 ml/min with a Ringer solution containing 5% dextran did not cause tongue edema, but perfusing at the same rate with Ringer without dextran caused edema. After perfusion at 0.05 ml/min with 100 mM K Ringer, the membrane potential of taste cells gradually decreased and reached a constant level in about 30 min, indicating that the intercellular fluid of the tongue could be replaced within this time period. While the artery of the frog tongue was perfused at 0.05 ml/min with Ringer containing 5% dextran, intracellular receptor potentials of taste cells elicited by four basic taste stimuli (1 M NaCl, 10 mM quinine-HCl (Q-HCl), 1 mM acetic acid and 1 M galactose) were similar to those obtained from the control taste cells under normal blood flow.     

Production of transgenic fish: introduction and expression of chicken delta-crystallin gene in medaka embryos

To produce a model of transgenic fish, recombinant plasmids containing chicken delta-crystallin gene were microinjected into the oocyte nucleus of a small teleost, medaka (Oryzias latipes). About 50% of the microinjected oocytes developed to 7-day-old embryos. By Southern blotting delta-crystallin gene was detected in 4 of 8 embryos, and, by Western blotting, delta-crystallin polypeptides in 5 of 16. In 1 of 6 examined histologically, delta-crystallin DNA was detected in all the tissues, and delta-crystallin polypeptides, in many of the tissues including the lens. Thus, the exogenous gene and/or its products were detected in 10 of 30 embryos examined. This is the first report of successful production of transgenic fish.     

Haemolysis of rabbit erythrocytes by a lectin from the seeds of<Emphasis Type="Italic">Croton tiglium</Emphasis>

The kinetics of haemolysis of rabbit erythrocytes byCroton tiglium lectin was studied as a function of concentration of the lectin and erythrocytes. The length of the prelytic period decreased with increasing lectin concentrations, indicating that the secondary events at the membrane which follow the binding of the lectin to cell surface carbohydrate receptors are accelerated at higher surface concentrations of the lectin. The rate or extent of haemolysis was not affected by the inclusion of ions like K⁺, Ca²⁺ and Mg²⁺ in the medium or by the substitution of ionic medium by a non-ionic medium. The inhibition of haemagglutination and haemolysis of rabbit red cells byCroton tiglium lectin by antilectin rabbit serum was observed. A possible mechanism of haemolysis by the lectin is discussed.     

Plant lectins specific for N-acetyl-β-D-galactosamine

N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus).