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.     

Two-step regulation of ecdysone-inducible late puffs in salivary glands of Drosophila melanogaster

Our previous study showed that some ecdysone-inducible late puffs could also be induced by a mild detergent (digitonin) in Drosophila salivary glands. However, they could only be induced at the stage immediately prior to when developmentally programmed puffing occurred, suggesting that these late puff loci were under two-step regulation. Using an in vitro culture of salivary glands, we have examined whether ecdysone or the protein products of early puff genes participate in either of the two steps of late puff regulation. This study has revealed that (i) the acquisition of digitonin-responsiveness (the first step) could be induced in vitro by incubating salivary glands with ecdysone; (ii) the first step could also be induced by protein synthesis inhibition even in the absence of ecdysone; (iii) the second step required both ecdysone and protein synthesis unless treated with digitonin; and (iv) the first step, rather than the second step, determines the timing of normal puff formation in the loci. These results suggest that, during normal development, ecdysone controls both steps by activating two types of early genes; the first type, whose function can be mimicked by cycloheximide, renders the loci responsive to digitonin and the second type, whose function can be mimicked by digitonin, activates the loci to form puffs.     

Comparison of the substrate specificity of the two bacterial desulfurization systems

Using cell-free extracts of a desulfurizing mesophile, Rhodococcus erythropolis KA2-5-1 (the Dsz system) and Escherichia coli JM109, which possesses the desulfurizing genes of a thermophile Paenibacillus sp. A11-2 (the Tds system), the reactivity of desulfurizing enzymes toward 4,6-dialkyl dibenzothiophenes (4,6-dialkyl DBTs) and 7-alkyl benzothiophenes (7-alkyl BTs) was investigated. Both systems desulfurized all the 4,6-dialkyl DBTs, except 4,6-dibutyl DBT. Although some alkylated BTs were degraded by the Dsz system, no desulfurized compounds were detected. The reactivity of the Tds system toward alkylated BTs was higher than that of DBT. In contrast to the Dsz system, the Tds system yielded desulfurized compounds from all of the alkylated BTs examined.     

Immunocytochemical localization of secretory acetylcholinesterase of the parasitic nematode Nippostrongylus brasiliensis

Various parasitic nematodes secrete acetylcholinesterase (AChE). In this study, the localization of AChE in the nematode Nippostrongylus brasiliensis and the secretory forms of AChE in culture fluid were examined. A thiocholine method revealed that AChE activity was localized in the subventral glands, which have a secretory and excretory function via a duct connected to the excretory pore. By electron microscopy, AChE activity was found mainly in the matrix of secretory granules, and sometimes in the Golgi apparatus in the subventral gland cells. These results show that nematode AChE is produced and stored in the subventral glands. Monoclonal antibodies against AChE of human erythrocytes or electric rays also bound to the nematode subventral gland, suggesting immuno-cross-reactivity of AChE among these species. When AChE activity in the nematode excretory-secretory product was examined by SDS polyacrylamide gel electrophoresis combined with the thiocholine method, intense activity was demonstrated as a single band at 74kDa. Immunoblot analysis showed specific recognition of this molecule by IgE and IgG1 antibodies, but not by IgG2a antibody, in nematode-infected rat sera. These results indicate that the nematode AChE molecule produced in and secreted from the subventral glands is antigenic for the production of IgE/IgG1 in host animals.     

Phylogenetic relationship of medicinally importantCnidium officinale and Japanese Apiaceae based onrbcL sequences

Cnidium officinale Makino is important medicinally and economically, but its origin is uncertain. The phylogenetic relationship ofC. officinale is provided from the analyses based on the ribulose-1,5-bisphosphate carboxylase/oxgenase gene (rbcL) sequences of 41 species which represent the 34 genera of Aplaceae, the four genera of Araliaceae, and one genus each of Pittosporaceae, Cornaceae, and Caprifoliaceae. The strict consensus tree obtained supports a close relationship ofC. officinale to the Chinese members ofLigusticum, especially toL. chuanxiong. Additionally, the tree shows (1) polyphyly of the genusLigusticum and (2) monophyly of the subfamily Apioideae. Within Apioideae, we recognized some groups in our phylogenetic tree. The grouping is discordant in several respects with the traditional tribal divisions based mainly on fruit morphology.     

Isolation and identification of (2S)-2-amino-5-chloro-4-hydroxy-5-hexenoic acid from anAmanita of the sectionRoanokenses (Amanitaceae)

A chlorine-containing non-protein amino acid which was recently discovered from the fruit bodies ofAmanita gymnopus (2S)-2-amino-5-chloro-4-hydroxy-5-hexenoic acid, was isolated and crystallized for the first time from the fruit bodies of an unknown member ofAmanita belonging to the sectionRoanokenses, subsectionSolitariae. The results of elementary analyses, determination of optical rotations,¹H- and¹³C-NMR-spectra, and some chemical reactions supported an earlier proposed structure.Part 24 in the series Biochemical studies of nitrogen compounds in fungi. for Part 23, see Hatanaka, S. I. et al. 1994. this journal35: 391–394.     

Intraspecific variability of Brachionus plicatilis

An extensive study of frontal margins of the lorica of Brachionus plicatilis was undertaken in an attempt to define its variability within this species. Specimens from mass cultures and from the natural environment were examined.     

Effect of temperature on growth and nitrogen mineralization of fungi and fungal-feeding nematodes

Dish and column microcosms containing alfalfa-sand medium were established to determine effect of temperature on growth and N mineralization ability of two fungi (Rhizoctonia solaniand Botrytis cinerea) and two nematodes (Aphelenchus avenaeand Aphelenchoides composticola). The microcosms were incubated at 15, 20, 25 and 29 °C for 21 days. In the dish microcosms, hyphal growth rates of both fungal species increased with temperature in the range of 15–25 °C. Above that temperature range, the growth rate of R. solani remained almost constant while that of B. cinereadecrease considerably. The population growth rate of A. avenae increased with temperature between 15 and 29 °C on colonies of R. solani and B. cinerea in dish microcosms. The growth rate of A. composticola also increased in the range of 15–25 °C but decreased greatly beyond that temperature range independent of the fungal species as food source. Inorganic N (NH₄ ⁺ + NO₃ ^–) was collected from each column microcosm by leaching every 3 days. In the columns containing R. solani, there was a significant effect of temperature on the amount of N detected in the fungus+A avenaeor A. composticolabut not in the fungus alone columns. The total amount of N was greatest at 29 °C for A. avenaeand at 20 °C for A. composticola columns, concurrent with the population growth rates of the nematodes. In the columns containing B. cinerea, the effect of temperature on the amount of inorganic N was not significant in either the fungus alone or fungus+nematode columns, although the population growth rates of the both nematode species were highest at 20 °C. For B. cinerea, the N amount across temperatures was the same or larger for the fungus alone as for the fungus+nematode columns. In general, the contribution of fungal-feeding nematodes to N mineralization was small in any combinations of fungus and nematode species at any temperature. Similarity in C/N ratio of the fungal and nematode biomass, organic substrate C/N ratios too low for measurable increase in net mineralization by the nematodes and small reproduction of the nematodes in the column microcosms were probable contributory factors.